The Steam game 'Team Fortress 2' runs laggy and choppy for me. I previously used an Nvidia GeForce GT 240 graphics card, with updated drivers, and this game ran with good frame rates. Now, the performance ranges from excellent to severe, usually resting somewhere in between. It depends on what I look at in the game. I've been experiencing this problem with almost all of the Source games I've been trying with this video card.
Anyway, I still want to acknowledge all of the great progress the AMD Linux team is making with the drivers.
Ubuntu 12.04.4, 64-bit
Unity Desktop Environment (vanilla)
Asus M4A78LT-M LE Motherboard
Asus BIOS Version 0803
AMD Athlon II X4 645, 3.10 GHz
AMD Radeon HD 6790
Catalyst Control Center Version 2.20
ATI/AMD Proprietary FGLRX Graphics Driver (**Experimental** Beta)