I expected it to be (much) better.
Unfortunately, I didn't research it; I relied on the reviews and the "name".

I'll start with the negatives:
1. If the cameras are on another network/subnet (with communication available, no firewall, etc.), they simply don't work properly. Or if they do work, for some reason they don't record. Live view works.
2. Tapo cameras work with ONVIF. It doesn't see them as TP-Link, and if you add them as RTSP they still don't work properly. So you lose various features (2-way audio, LED light, etc.).
3. Anyone who has used a Zoneminder or a Synology Surveillance Station will be very disappointed. The web interface is terrible and poor, and the configuration options are very limited. The PC app is a bit better; the mobile app is a bit more usable, although with even more limited settings.
4. Audio in live view doesn't pass through. However, it is recorded. - Edit: Ok, now it does pass through with the latest updates.
5. You can't export events from the web interface. From the PC it's more difficult but possible. From the mobile app it's somewhat better.
6. Motion detection sensitivity is almost impossible to adjust. I didn't notice any difference with any setting.
7. Human detection or whatever else Tapo cameras do, the NVR doesn't see it. Its own detections don't work with ONVIF/RTSP. They do work with Vigi cameras though (and generally the integration with Vigi cameras is good).
8. Live view from Firefox does NOT work. It works from Chrome (but not always; even though I've already loaded the certificate on the PC, it sometimes asks for confirmation). - Edit: Now it also works from Firefox.
9. In general, many of the features (most of them probably) don't work. They require Vigi cameras exclusively.
10. Ah, with HDMI, when I tested it on a 4K monitor, the two cameras I was viewing were on the 640x480 stream, resulting in terrible image quality. I don't know if it changes; I didn't look into it much. - Edit: Ok, this too improved with updates.
11. Finally, at least with Tapo, it doesn't support two-way audio.

Positives:
1. It's silent. It doesn't have a fan; I also put in a 5200rpm drive and it's fine. Just make sure to disable the buzzer it has too (fortunately you can configure that quite a bit).
2. You can also view it from the cloud if you enable it. Useful feature.
3. The quality doesn't drop much; I didn't notice anything in tests with two Tapo 2K cameras. Edit: 2 Tapo, 4 Vigi, 1 no-name, they work just fine.
4. If you set it to record 24/7, it will probably perform just fine.
5. It has HDMI and you can connect it to a monitor and control it with the mouse (included in the box). Useful for some people probably (I just tested that it works; I'm not interested, I put it in a corner and left it there).
6. The package also includes screws for the hard drive, etc. By default it takes only 3.5" drives (although I don't think there's any reason to use a smaller one; it doesn't change anything).
7. It's very lightweight. Basically inside it just has an all-in-one board where the drive plugs directly in.

What I would like:
1. Support for cameras from other companies too (well, for TP-Link I won't even discuss it). So you don't have to look up ports, etc. (although for RTSP/ONVIF that's pretty much default).
2. It should be able to send logs to a syslog server. It had one reboot and I don't know why. - Edit: It still doesn't send to syslog (while Vigi cameras have this capability).
3. Better sensitivity adjustment for recordings (motion detection).
4. Two-way audio!

Would I buy it again?
No way, not even as a joke...

It connected relatively easily and 4 cameras were attached to it. Settings via mouse and silent. The cameras that were connected were 2 Tapo C320ws and 2 Tapo C210. Very satisfied. Through the app, there is the possibility of remote monitoring via mobile. It comes without a hard drive (like most recorders), so count on an extra 40-50 euros for a hard drive. IT SUPPORTS 3.5 INCH hard drives and not 2.5 inch, the screw bases require a 3.5 inch hard drive to fit properly. I chose a WD disk, the model HDD WESTERN DIGITAL WD23PURZ PURPLE SURVEILLANCE 2TB 3.5" SATA3. Works perfectly and silently. Supports hard drives up to 10TB and is eight-channel, which means up to 8 cameras can be connected to it.
UPDATE: Another recorder was purchased for another space with the installation of 4 new cameras. Very easy to use, many settings in its menu even for the most demanding customer. The only thing I would like is a Greek menu (for those who do not know English). Maybe this will be solved with a firmware upgrade.
USEFUL TIP: Tp Link recommends WD Purple 24/7 hard drives for its recorders. They have the ability to record 24/7 seamlessly without generating heat or noise

I bought it for a small NVR system with 4 TP-Link cameras. I would say it is a decent to good product. It is relatively small in size, although it could be much smaller if instead of being designed to accommodate a 3.5'' HDD, it was for a 2.5'' SSD. I installed a Samsung 870 Evo 512 GB and it recognized it immediately, as well as the TP-Link cameras. However, the installation of the SSD was not easy because it had holes for screws only for 3.5'' HDD and without including an adapter. Fortunately, one of the holes matched, but I consider it unacceptable not to have support for 2.5''. I haven't tried other cameras, so I don't know if they work, but based on the specifications, I don't think there will be a problem. This particular model, as well as the larger 16-channel one, does not support PoE. However, TP-Link has released models (obviously more expensive) with an integrated 8-port PoE switch. The software is also average, clearly much inferior to the one provided by TP-Link in the cloud, perhaps intentionally to make you pay subscriptions, as it does not support any of the advanced features like person recognition, intrusion recognition, and line cross recognition. It only supports motion detection, which is also very sensitive without significant sensitivity adjustment. Another thing it lacks is good disk space management. You either use the whole disk or none at all. This is not a problem for HDD, but for SSD it would be good to have the option to use a little less, which would help prolong the disk's lifespan. Another problem is that the management through the Vigi app contradicts the Tapo app. The settings of the latter override the settings of the former, to the point where it may not work. Although its performance is very stable and with low power consumption, I believe TP-Link still has a lot of work to do to improve this product. However, its price is very good, which improves things a bit.