The entire consensus seems to be for Nvidia, is it is closed but will generally work. You are against practicality but don't judge me if I go with it. That's not fair.
My beef with ATI is the low resources given to it by AMD while claiming to have 'good' support. Four developers for the FOSS driver and then there's applause because they might hire one more? Congrats.
They are getting closer to the binary Nvidia blob with their own binary blob. Good. But, the gap with Windows is still wide and large. Support is not same day release like it is with Nvidia and I am talking about the binary.
Just because I am desiring more resources given doesn't mean I support no open source options or Nvidia's policy. I am more than annoyed with the Optimus situation so that if I buy a laptop, I will not pick any Nvidia solution.
If I complete the build of my 2nd machine, I will buy an ATI card so that I can test it. Kano is right in that respect, it's way better to conduct tests with another machine. Especially if it's two 'different' cards.
Anyway, I have said my two cents and don't want to argue anymore. I know there's a good mix of perspectives here so I'll let them continue.