Xiaomi Mi3 is a great product and I am using this phone from 2 yrs. The phone looks premium with Mi claiming the back is made of Aluminium.Coming to performance of this phone
1) Camera Quality- It uses a Sony camera sensor which is above average.Indoor shots are a bit grainy but outdoor shots are really good. The camera interface is simple but Manual Camera mode can also be accessed.
All in all a great Camera.
2) Multi Tasking-Thanks to the 2GB RAM phone runs smoothly with a lot of apps running in the background.
3) High Quality Videos Playback- Full HD, 2k and 4k videos run without any issues. But storage limit is a con.
4) User Interface- Easy to use UI called MIUI which resembles Apple’s IOS never lags.The response time low and apps open fast.
5) Gaming- High Quality Games like Asphalt 8, MC5 etc. run smooth without any frame drops.
6) Battery Life- Last but not least , battery life of this phone is quite good. I play lots and lots of heavy games daily and still some juice remains unused.Thanks to the 3000 mah battery.