FYI for other users: installing Gnome3 via UGR (http://ugr.teampr0xy.net/) will break your unity install.
Ubuntu (and Unity) is still Gnome2-based (I haven't heard anything, yet, concerning a move to Gnome3 for a future release).
So upgrading to Gnome3 is a one-way upgrade and will break your Gnome2-dependent environments. Although I've done a ppa-purge to uninstall the UGR packages and things seemed to have gone back to normal, pretty much.
