Anyway, back on topic. ATI's method at the moment is 3rd party drivers from iZ3D and TriDef (DDD) where ATI's Open Source is to allow iZ3D and TriDef a proper look into its drivers, and thus optimise for ATI. Which, I can't help but feel is a touch on the lazy side...
The two drivers have strengths and weaknesses, but overall I think the TriDef come out on top. They are both limited to DX9 at the moment, but both support a wide array of setups (from shutter glasses, screen polarisation etc), although the TriDef drivers just have some nice features, such as 2D-3D film conversion (which works surprisingly well).
I find 3D in games adds a new level of immersion, but it has to be the right game. In MW2, the effects are excellent, but I'd find I'd feel ill after a while with the flicking, and fast-paced nature.
Burnout is excellent in 3D, adding depth to the cars, and when you crash through barriers and such, they feel as though they are flying over your head.
So, it depends on the game really.