I have a C7-00 and recently upgraded to Belle. There are both minor and major bugs with the new OS. Following issues encountered by me like :

Battery indicator oblique after power saving mode icon activated- battery left to be shown in % terms, as available in earlier version..

battery guzzler..seems that battery lasts less than before..

After opening the messaging app, it opens only the conversations view. Option to view sms in folder view not there..

Icons/shortcut to forward sms is missing, though reply & delete icons are there

Sms notification widget is missing..

Nokia, please give us a user-modifiable icons & settings..it is defeating if user friendly options are curtailed in new version..rather there have to more additions..