don't know which miui version (stable or developer) i am using...i took the ota from v5...I downloaded supersu from chainfire's site...went to recovery and applied update...followed steps from this thread....http://en.miui.com/thread-39251-1-1.html
Thanks! Got into a little trouble with google play services force closing and root missing intially...finally after 3 hours got v5 working and then updated to v6 via ota...root is still a problem though...