A lot of people have remarked that the open source drivers work better than the closed source drivers. This is not so for HD7xxx. My HD 7950 gets stuck smack in LLVM Software Rendering and thus TF2 or any other game I try to play can't even render at 0.1 FPS. The Catalyst 13.6 driver at least gets 19-29FPS with a bit of lag spikes here and there at random intervals in TF2. CSS/DODS get really low framerates as well, but these aren't very graphically demanding as, say, TF2.