I bought the v3 of the Access Point and I am completely disappointed.
Initially I use it as a Router on Cosmote with fiber connection which means it connects directly to the ONT and makes a direct PPOE call.
While it works for about 20 days, suddenly it crashes and with a restart it doesn't come back up. I need to leave it off for about 10 days for it to work for at most a month.
Additional strange/problems:
- It has a very poor web interface without even the ability to export logs, you can only view them and copy them with pagination every 10 errors. Generally, you mainly see only the status.
- The range is okay, like a router with 6-8 antennas, at least that's prettier (when it works).
- It doesn't have backup/restore settings which means that in problems like the above if you need to reset you have to redo all the settings from scratch.
- For some reason, in the Deco App, it doesn't correctly record the upload of devices while the download works fine.
I did not expect that the Mi Router I had before would be more stable than a TP-Link. Also, I expected that in equipment that is fully configured with an application, the settings of the providers would be ready, especially when there is a Greek representation behind it and the device is resold by the provider, but of course it does not apply and you have to figure out the settings, especially on Cosmote.
1/5 due to stability and cost.

I purchased 4 units of DECO X20 V4, which is the latest hardware version, in order to create a MESH Wi-Fi network in a four-story house. One unit was placed on each floor to ensure sufficient coverage, which indeed exceeded my expectations in terms of coverage and speed. However, the peculiarity is that all DECO units were connected to each other via ETHERNET BACKHAUL (the DECO units are connected to each other through a network cable https://community.tp-link.com/en/home/forum/topic/98898).
The DECO units have the ability to function either as a router or as an access point.
As a router, they introduce some limitations. They use the subnet 192.168.68.xxx with a subnet mask of 255.255.252.0. I couldn't change it, even though there was a possibility, to 192.168.1.xxx / 255.255.255.0 due to the incompatibility of the ISP router's network categorization (FORTHNET in my case). Due to the presence of several devices with static IPs in my case, the process of changing network settings, gateways, and open ports would be a headache. So, I chose the function as a simple access point. In this case, there are no features such as Home Care, Parental control, Antivirus, etc. Personally, I do not consider it a problem because all these can be covered, perhaps even better, with other related programs (except that, as mentioned in another evaluation, a subscription is required).
In Access Point mode (using the ISP's router as the main router), the performance is excellent, with the only downside being the lack of ability to set static IP addresses on the DECO units for comprehensive network management (this feature is available in regular access points).
The initial setup through the DECO app for mobile phones is easy and fast. In case the DECO devices are connected to Ethernet Backhaul, they should be configured wirelessly first and then connected via cables.
The application is user-friendly and provides sufficient information and capabilities, but it could be improved with perhaps more features.
Connection through a web browser is possible, but the information and capabilities are very basic.
The cost for Wi-Fi 6 mesh, at the present time (4/23), with some promotional activity through skroutz, is around 240€ for 4 units of DECO X20 V4, which personally seems moderate to me.

Today I received the DECO X20 with the purpose of adding them to the existing DECO network I have with 4 DECO M5. The reason I decided to try the DECO X20 is for the higher speeds and possibly greater range due to dead spots I had, as well as for the wifi 6. The house is a four-story detached house. The first move was to replace the main deco m5 with the new X20. Once I installed it, I noticed the following differences: 1. There is no option to prefer Deco connection. 2. To set schedules and separate weekends from weekdays in parental control, I have to become a subscriber to Deco. 3. Security control, etc., again through subscription. As soon as I understood what was happening, I immediately put back the old M5 and all these features were free and standard. I tried using an X20 as an extender and comparing it to the corresponding M5 in terms of speed and range, and there was no difference. In the end, they went back in their box and maybe I will use one as a satellite in the future. CONCLUSION: DECO M5 is superior and more reliable. Stay away from DECO X20.

Amazing! I got it plain (1 pack) to complement the other two identical X20 units I had in a 3-level house (about 90 sqm each level) with concrete slabs, double-brick walls, insulation, and plasterboards. The whole house has been covered with a single WiFi name (2.4 and 5), all devices (mobiles, tablets, laptops) that move from floor to floor automatically know where to get signal from and you don't even notice it! I have a hundred Mbps line, the first one gets internet through a cable from the provider's router and provides a hundred Mbps WiFi on the floor it is on (maybe drops to 80 meters away) and on the other floors depending on the distance from the corresponding Deco unit, it is 30 - 80 kbps. I found my peace, I removed all the repeaters that were driving me crazy with interruptions and poor speeds, as well as all the powerlines in the house. I completely silenced the WiFi provided by the provider's router. Don't wait at all. Get it. Each Deco has 2 ethernet ports to connect a Smart TV or whatever you want. It also provides a Guest network so you don't have to put your guests on the home WiFi. Nice thing!

Usage: Replacement of older Netgear Extender. Integration of Deco network for stability and collaboration optimization between TP-Link products.

I am not using it as a router (I still have the M5). However, I have set it up as a central channel between the M5s. The router is on the 3rd floor. This product was installed on the second floor. The line shows slightly higher delays compared to the previous equipment. However, packet loss has been optimized. It also eliminated two blind spots. The only problem I have is that its firmware does not yet support non-roaming mode (to explain, with the M5s, I can "pinpoint" where they receive signals unlike the X20, which still does it on its own). I do not yet have an extensive opinion on its durability under difficult conditions and demands. However, I will say that for simple use, it is an excellent purchase.

26/5/23: Unfortunately, its firmware has not been updated for the issue I mentioned above. In high-pressure flow conditions, it shows minor losses, but they are not significant enough to destabilize the connection. However, during restarts (every 8 hours is my setting), there is a possibility of it taking longer to connect. I believe it is a mesh issue rather than a device issue, but I consider it worth mentioning.

The review is for the 2 Pack.
I bought it on 19/02/21 from a large store for 230 euros.
I live in an apartment building where I have the provider's router on the 1st floor with a 50 Mbps connection, and on the 2nd floor, where I spend most of my time, I barely had a signal.
So, about 4 to 5 years ago, I decided to buy my first Tp Link Extender and place it on the 2nd floor.
The job wasn't done properly, so after 1 or 2 years, I bought a second Extender, which was placed on the 1st floor to increase the signal on the 2nd floor.
The signal problems continued, so the purchase of a second Tp Link router with 4 external antennas became necessary.
The second router was connected with an Ethernet cable from the provider's router to the 2nd floor (as usually the provider's routers have signal transmission problems due to lack of external antennas), and this somehow improved the speed on the 2nd floor to around 42-44 Mbps download and 4-4.5 Mbps upload.
The speed was satisfactory, as many would say, but there were other problems such as:
1. I had to run a 20-meter Ethernet cable inside the house, which was unsightly.
2. The Tp Link app that supported the router did not support one of the two extenders (the extenders were different models), resulting in occasional connection issues.
3. Whenever I moved to a different floor or room, I had to turn off the Wi-Fi on my device and turn it back on to connect to the nearest router or extender.
4. In our house, we have at least 10 devices, some on 2.4GHz and some on 5GHz, which the extenders did not support, resulting in almost all 10 devices working on 2.4GHz, increasing Wi-Fi interference.
5. Weak signal in dead spots on the 2nd floor.
6. Devices would sometimes get stuck on download even though there was a Wi-Fi signal, possibly due to interference.
Now let's move on to the present.
After receiving the product and opening the package, I was initially impressed by the size of the Decos, their sturdiness, quality, and beauty.
Even the packaging itself is of high quality, as we are accustomed to from Tp Link.
The package contained the 2 Decos with their 2 chargers, an Ethernet cable, and the relevant instruction booklets.
I should also mention the 3-year warranty from Tp Link.
After installing the first Deco with an Ethernet cable on the provider's router according to the instructions, the installation took me no more than 3 minutes through the Deco app from the Appstore.
For the second floor, which interested me more, I installed the second Deco, which was installed within seconds through the app, and voila!
I had full Wi-Fi signal throughout the entire 2nd floor, in every corner, without any wiring from the 1st floor.
We're talking about a 90-square-meter duplex, each floor.
I also tested it outside the house and had a signal in the middle, 50 meters away from the house.
After programming it for about 5 to 6 hours and while everything was working perfectly, there was a power outage in the evening.
The next day, I found out that one of the two chargers for the Decos had burned out. I want to emphasize that it was on a high-quality Apc surge protector, which I had never had any issues with for 6 to 7 years. Only the charger burned out, which means it was a faulty charger or not of good quality, which does not justify the 230 euros I paid, and here I give Tp Link one minus star.
After calling the big store of my purchase, they asked me to send them the whole package to be checked, not just the charger, and after it is checked, they will see if it is covered by the warranty to send me a new one. We are talking about a process of at least a week, during which I would have to set up the whole previous setup again, run 20 meters of cable, and configure 3 different models of Tp Link, which is time-consuming. In the end, I managed to do my job with a Laptop charger (it has the same plug as the Deco charger) and everything works as it should.

Now let's move on to the many positives that this system has:
1. With the previous setup, I was getting 42-44 Download and 4-4.5 Upload on the 2nd floor with an Ethernet cable from the provider's router, while with the Decos, I get 45-48 Download and 4.5-5.5 Upload, all WIRELESS from the 1st to the 2nd floor. On the 1st floor, the internet literally ends with higher speeds than what the provider offers.
2. I have full signal everywhere in the house, on both floors, and it only starts to drop if you go outside the house at around 50 meters.
3. With the previous setup, I had to toggle the Wi-Fi of the device on and off to connect to the nearest Router-Extender, which ended with the Decos as they have a smart function and automatically connect to the nearest Deco (although it takes a few seconds for the change to happen and it's not instantaneous).
4. The Decos automatically select the best frequency for each device, so now my modern devices connect to 5GHz and the older ones to 2.4GHz, which automatically reduces interference in the space.
5. The app can support up to 10 Decos and 150 connected devices, which makes it suitable even for professional use!
6. The system provides antivirus and parental control, fully customizable, but I didn't delve into it further.
7. The app, through pop-up notifications, informs you in real-time on your mobile about which device connected or was connected, on which frequency each device is running, and to which exact Deco it is connected.
8. You can block certain devices from accessing your network through the app, prioritize the devices you want, i.e., have them consume more data volume than others.
9. It supports Wi-Fi 6 or 802.11ax, which makes it much faster than Wi-Fi 5, although it hasn't been tested as I don't have a device with Wi-Fi 6.
10. Each Deco has 2 Ethernet ports, which is more convenient compared to the Extenders that had only one.

In short, I got rid of cables and unnecessary devices scattered around rooms in the hope of catching Wi-Fi. I consider it the best solution, guaranteed, because even though I paid almost triple the amount compared to the previous setup, I have better and stable speed, and all this is done through an app that supports up to 10 devices.
I am already preparing to buy a second set for another house, even if it's expensive and even if the charger turns out to be defective. You can do your job with €10 chargers from the market. What are the extra €10 compared to all the hassle you have been dealing with for so many years? Buy without fear!

Update: 5/4/21
There have been at least 2 to 3 power outages, and probably others that I haven't noticed while sleeping, and the decos and my second charger are working fine, which means that the first charger was defective.
The charger of the Laptop still works perfectly as a backup.
As for the decos, I have to say once again that it has been a lifesaver for me.
I fully utilize all the functions, including the virus protection it offers, which is indeed efficient.
With the recent update, Tp Link now also supports smart devices.
I have Philips Hue equipment and now I can control the lighting through the application.
Congratulations to Tp Link for the support, choose it because it is a recent product and since it supports Wifi 6, I believe that Tp Link will bring new things frequently through updates.
Update: 27/4/21
Because I read comments that there is no option to choose between 2.4 and 5 frequency, the possibility exists to do it manually (More, WIFI, and there you choose 2.4 or 5 or both), but you will either have 2.4 on all devices with the risk of interference or 5 on all devices, resulting in older devices not having internet due to lack of support.
So the best solution is to leave it as it is and let it automatically select the best frequency for each device.
I agree that it takes time to make the change, maybe it will be fixed in the future.
Do not misinterpret it if you don't thoroughly investigate it.