We've learned that RV770XT and Pro won't do Full Scene Antialiasing via Shaders. Developers hated it, but RV670's design flaw was responsible for it.
RV770XT and PRO will end up significantly faster, especially with FSAA compared to RV670 generation. The numbers should be higher than you usually see from generation to generation, but we don’t know more details about it at press time.
RV670 was improved and fixed R600, or should we say R600 was done right, whereas RV770 is an improvement of the stuff that ATI has implemented.