I've got it working with catalyst 12.8 on Ubuntu 12.04.2 but the driver breaks quite a few things in Ubuntu.
Catalyst 13.3 beta 3 works great with Ubuntu 13.04 beta!!!! But when I open the miner it claims there is not GPU present at all! :/
Any ideas?

EDIT: My setup is a 7750 at 880mhz pulling 133.3mh/s with the 12.8 on 12.04.2.