Coming from MIUI 4.8.8 (multilang, based on 4.4.2), I did install MIUI 4.8.15 (from january73's post #211, based on 4.4.4) with only wipe-cache and wipe-dalvik-cache - keeping my /data intact, and everything seemed to work well. After approx. 1-2 hours I remembered I did not reactivate (reinstall) WSM framework - and found out, that it can't be installed. So I went back to a CWM backup of MIUI 4.8.8... but in the short time I had the 4.8.15, I did not have any problems...
I explicitly don't trust OTA updates. Prior to any update I do a backup in CWM, so that I have something to return to, in case of problems...