Purchased in Big Billion days (Oct 2015). Felt its pretty worth for money I spent for this mobile.

Good points:

1) Pretty Handy and Small, Cool looking due to colour variants.
2) Very Soft touch screen
3) Charges to 100% within 50mins (*when Wifi / Bluetooth turned off [or] in flight mode)
4) Rear camera photo clarity and even when zoomed is outstanding. (without flash)

Issues found:

1) Selfie camera is not capturing image in reverse (Absolutely disaster from Day 1). This problem is with...

- Display good with good clarity.
- Camera quality is pretty good compared to price. Got this phone at around 5500 with discounts.
- Got this phone for my wife who is not into gaming that much. but while playing standard games like Subway surfer i found the phone lags a bit which is not expected as Xiaomi boasts it is Octacore.
- Battery is good gets more than one day easily.
Overall a good package for moderate user.

I bought it during the great Diwali offer..good price @ 9999/-
Good quality... battery lasts for 1.5 days with decent usage. Camera Good... !
Sometimes... i get google play services stopped... i don;t know.. yet to consult somebody.
After 3 weeks of use, I am a happy user.

Review & Rating of Mi4i, used almost a month now:-

Purchased it from Flipkart, on time delivery. 5/5
User Friendly Mobile User Interface. 5/5
Amazing Picture Quality with a Decent Camera. 4/5
Gets a little heated up upon playing heavy games like Asphalt, which i guess is common with most of the mobiles. But as it is i dont play if for long hours, hardly 15-20 mins or max half-n-hour. 4/5
Nice Music in earphone/headphone. But little Low sound thru back speakers, sometimes even missed calls. B...

I am writing this review, keeping advanced users in mind.
I got this phone around 15 days ago, and rooted it on that day itself. Flashed a 5.1.1 Lollipop ROM.
Camera :- Too good, coming from Redmi 2, the camera is definitely an upgrade and fancily carries itself as a USP for this device.
Internal memory :- Now this is where Xiaomi dissapoints. Out of 16 GB, a meagre 11 GB is available. That remains a serious drawback for advanced folks who are accustomed to carry multiple ROMs in internal mem...

Just a awesome phone within 10k . Stunning display , Brilliant Camera, Good Battery backup and one more thing there is not that much of heating problem i am using this phone from last 7 days and i am not facing heating problem and i am using UI7. Just upgrade and enjoy and buy Mi4i within 10k

I have been using Mi 4i for few months now and till now not faced any problems, detailed and honest review.
Pro's:
1. Excellent display (Comparable to IPhone6)
2. Excellent Camera (You wont believe but the color composition is even better than DSLR camera's)
3. Speed is good (processor and RAM).
4. Physically hard mobile and good design (Many times it has fell down on ground but nothing happened, also has great resistance to water)
5. Express charging available.
6. MIUI latest version is sup...

Best product at competitive price. Having such a great features it beat 30k-40k price range smartphones. I'm overwhelmed with this mobile and it's features.... Thank you.

Yellow colour is very different and looks very trendy. Great device. Better then HTC, Moto etc.
Camera is too good.. especially front cam, it takes very nice selfis. Lag free and doesn't heat up in normal usage. battery lasts for 2 days

Got this awesome phone in just Rs.8999 during festive offer. Have been using it from almost 2 months. positive sides of this phones are:

#Slim Elegant Look
#FHD Display
#Awesome Camera Quality
#Nice Battery Backup

Negative side:
#No Expanding Memory(only 10 gb accessible)
#Non removable battery

Didn't find any other issues...i'll update if found anything in future