As we already wrote, you can get up to a 15 percent performance boost with DirectX 10.1 in H.A.W.X. and according to the video at Youtube, you can get up to 30 percent in some titles, for example Stormrise and Battleforge. This video is done by ATI so take that 30 percent claim with a grain of salt, as they claim higher gains in H.A.W.X than those which we got during our testing. In any case, even if the gain is not 30, but rather 15 percent, it's still a great result and a great win for ATI.

They have some HAWX benchmarks here that show that the biggest benefit is with AA turned on.