The hardware is great, there are only two things I bother about.
1. It really should have had two side brushes. An entire wall simply does not get clean.
2. The mop function is totally unnecessary and would have preferred larger containers for dust or more powerful engine.
The app on the mobile is under all critical. It's the most buggy app I have on my mobile right now and it only gets worse with each update.
Sometimes you have to try up to 10 times to start the app before it even starts trying to call the robot vacuum cleaner.
Thresholds: It managed 2 cm before, but that is simply no longer true due to a major update that introduced room division, which means that the vacuum cleaner turns 90 degrees along the threshold (where the room ends) and gets stuck on the threshold with the wheels in the air. For unclear reasons, the robot chooses to vacuum ~ 1 dm outside the room, which * always * is along the threshold. I suspect this is due to the lack of 2 side brushes. A huge problem that would have been easily discovered if Xiaomi had a functioning QA department.
I have finally switched to thin sill tiles, so now the problem is out of the world in my current apartment.
Overall, it gets a weak 3rd, because I so rarely need to vacuum anymore. However, the frustration over how Xiaomi has chosen to support this model is palpable and will only get worse and worse.
And for god's sake, put the robot on its own isolated guest wifi, so that it does not have access to your other devices. All traffic is via WAN anyway.