I have the MI3 and MIPAD. It is very well known that MIUI is not well written for speed and is very sluggish compared to a clean android experience. But the quality of software on the MIPAD is another low altogether. There are so many hardware/software bugs and crashes. The one which bother me the most is the issue with the buttons at the bottom of the screen . They do not work most of the time . You will have to press several times or press it hard to work.
The "smartcover" mode is broken. It will turn off the screen even when you fold the cover behind the device. This will happen even if you tun off the smartcover mode.
The MIUI devs prioritize adding more features and the "look" of the UI rather than fix the bugs no matter how important the bugs are. This is proven by the fact that this device has been sold for almost 1 year and still so many bugs exist.