In 10.04 I had my system set up so that I could hover my mouse over a menu item and type a shortcut and that would be the shortcut for that item. To do this I had enabled
/desktop/gnome/interface/can_change_accels in the gconf-editor.
However, after upgrading to 12.04 this seems to have disappeared. The item is still there in gconf but it seems to have to effect.
I would really like this to work because it is a really neat trick that make my life SO much easier.