I installed the update through the developer preview yesterday - assume this is GDR3? Took a while, but all appears to be working fine. Not much has changed that I can see - driving mode, able to close apps easier. Can combine email accounts into one inbox.
I can now get BT to connect to my Windows 8 PC, but still can't get PlayTo to work.
I appear to have broken the music player for the time being. Probably related to the PlayTo problem.
I've probably missed stuff and some of the above may have just been missed before, but seems to be ok.