I'd have to disagree with the inference that the 9800's have more potential and that nVidia had to set their clocks higher to beat ATI because it seems to me that the 5900's have plenty of room left. Notice that the highest legitimate(real) score is owned by an nVidia card;
here's a link.
As more and more of the newer technologies are incorporated into games, the 5900's will only show more of its lead.