High profile ATI executives have told Fudzilla that ATI was looking into whether it's possible and beneficial to clock the Shaders at higher clock speeds than the GPU clock, and the engineers have decided that they cannot make it work on RV770 chips.
They will be investigating if this pays off, as ATI and Nvidia do Shaders completely differently; and if it pays off there might be a chance that ATI will clock its Shaders faster than the GPU clock. This is, of course, as of next generation, let's call it RV870.
This is currently the only big advantage that Nvidia has over ATI design, but at the same time ATI has more Shaders clocked at the GPU speed while Nvidia has less Shaders, but they work at much higher speeds than the GPU clock. One thing is sure, with its RV770 marchitecture ATI is certainly catching up, if not even winning, against the G92 concept.