I know from insider sources + techreport's own editor also agreed that the RV770 offloads AA to ROPs. The original design of the R600 was supposed to do AA in ROPs but it never worked properly so they were forced to write drivers that used shaders for AA.

Some ppl claim that this wasn't a big performance hit and it was the TMUs limiting the RV670 more than anything. That I'm not so sure about.