With those latest updates gdm is now working better than it has since I first began testing Raring + the staging PPA.
But I notice that gnome-tweak-tool once again fails to launch, and my previously installed extensions fail to work ............... oooh, uh, oh, just thought to check something
EDIT: I was being a dummy, I was logged into GNOME Classic
So logged into the standard GNOME session gnome-tweak-tool does launch okay, but it shows no shell theme, and therefore no extensions: