I have recently upgraded my graphics card from an Nvidia GeForce GT 240 to an AMD HD 6790. I had no problems with the Steam game 'Counter-Strike: Source' under the previous GPU. However, now, it seems that whenever there is water on a map, there is severe overall lag. I don't know if this occurs exclusively in this situation; there might have been one round where there was no water and it still lagged. The lag and choppiness is so pronounced, it is next to unplayable. However, the lag reduces momentarily when facing away from any pools of water.
Hope this will be addressed in coming driver releases. Regardless, thank you, AMD Linux team, for your work so far on improving AMD Linux 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 (Post-Release Updates)