I bought high end graphics cards from amd because I game under Linux, and Nvidia drivers are crap there. Or at least used to be, they are supposed to be improved now? But I already left that camp...
I'm planning to upgrade my Linux system with a new graphics card soon, and the only reason I'm actually still considering Nvidia is CUDA. It just seems so much easier, and so much more broadly supported by software. But maybe that's just because I've never tried it.