got my mi4i a week ago 32gb version (24.xxgb actually). bought from xiaomi website. so far:

1 - camera really nice. much better than redmi note 4g i use to have.
2 - rough comparison, redmi note 4g much much better performance. less lag than mi4i which is weird.
3 - seems like overheat zzzz
4 - not so smooth i wonder why, it should be better than redmi note 4g

gonna try miui 7 later. its in xiaomi website already (developer build i think) or maybe i should try other rom?