Just little helpful information:-
Hey guys i am on b6 and its running very smooth. ( IMO smoother than other miui )
you will face random reboot if you try to restore app from miui backup app, but i faced it once only, then i restarted phone and restored again.....and now i am not facing any random reboots, its running so smooth.
so those who are facing random reboot problem,they can try as i did above OR restore app using ultimate backup app.
and yes you will face random reboot on about phone>status ( where you used to get Fc, now china did improvement by replacing it with random reboot
those who are agree on this post, hit thanks or reply to it......so that i will come to know your opinion on this