Before you get *too* excited, realize the x1800xt is not out yet. The only cards being benchmarked were the ones ATI sent reviewers. If I was in ATI's shoes, I'd damn well hand-pick the chips which were used to make these cards, to make sure reviewers so inclined would get amazing results from overclocking.
Of course, I could be wrong, and ATI just decided to downspec their hardware by 20-30% because they wish to get an even bigger unsold product inventory on hand.
But I'm guessing once the cards are released, your mileage will probably vary.