The design of the Mi4 looks good with the stainless steel frame, though the back is made of plastic the phone seems well built. Lets talk pros and cons.
Pros:
1) Snapdragon 801 with adreno 330 is enough to run any games smoothly, and also ensures smooth ui performance.
2) Both cameras perform is very good in good lighting conditions and decent in low light, OIS is missing though. 4k videos can be recorded and clarity is good.
3) The non removal battery performance is good to get u through a entire day of moderate to high usage.
4) The phone has many sensors including IR blaster.
5) Miui is smooth and lag free.
Cons:
1) no external card slot so, if ur a heavy user then go for 64 gb version.
2) 4G is absent.
3) still stuck on android 4.4