I have noticed the recent posts for Gnome 3 problems all are answered "Install gnome-shell".
Could gnome shell be add as a dependency to gnome 3 core?
Before doing the updates and you find gnome 3 in list, do a search for gnome-shell and install everything listed (4 or 5 things). This will give you gnome-shell and tweaks plus system-monitor and couple of others.
This should save some grief and posts.
Some nice themes http://half-left.deviantart.com/