Hey Proto, been a long time man. I see you haven't changed!
What ATI card did you have before you changed? Did you upgrade your entire PC? Are all things exactly equal here?
Because your claims are complete BS man. If you had a card on the same level as your GTX275, it would have been an ATI 5870 or maybe a 4890. Otherwise, you are not comparing apples to apples here.
Guys with 5870's are getting very close to same fps at the 280's are IF all things are equal. Which they likely are not.
ATI's AA settings are way different than Nvidias as well as the quality. To get two games set up exactly alike would be tough because the AA settings alone just do not match up.
So, lets just get off the fanboy wagon here(I am one, I know it) and get back to the topic.