Yes, but with lots of tearing most of the time.2.Does compiz and video work correctly yet?
It was simple enough that even a potato could install it to begin with, so I really can't imagine what "simpler" means3.Has the installation process on Ubuntu gotten simpler?
With the closed source Catalyst drivers, yes. With the open source drivers, no, it's fine there.4.Are people still getting over heating issues with the cards, and linux drivers?
But instead of asking, you can just boot the latest live DVD; it will auto-detect ATI and fire up Compiz. If not, try the Sabayon Linux 3.5 live DVD (I tested it; it automatically loads the Catalyst driver and Compiz Fusion).