I have three machines running Ubu12.04 and all have been giving me serious problems - OpenGL not working -they are all NVidia.
I have been using XFCE in preference to Unity as Unity offers me nothing apart from easing a few management features.
After an upgrade yesterday I cannot run Unity at all on one machine - a 1 year old 4 core AMD.
I used to like Ubuntu now it seems to be the flakiest distribution there is.
I am going to re-install with Xubuntu to see if that is usable