I'm using radeon driver myself, but then on a legacy ATI mobility radeon X1300. (that's the reason why i'm stuck with it. ATI doesn't support legacy products anymore with recent kernels and newer xorg) It works and is playable performance-wise. Graphics do flicker sometimes, but it can be lived with.
As you have a 'newer' card, the only thing I can recommend is installing the official ATI driver (fglrx) either from the ATI website, or by making use of package manager.
Performance will be much better and you'll get support for everything PS needs.