The 9800gx2 is crap. It is essentially two G92 8800GTS' strapped together. No new technology is involved. Meaning, no fantastic gains in performance over current tech. I'm sorry but 30% is not worth the price they will charge for it. especially for people who game at high res, it only has 512mb of ram per core, so at high res, it may be a lot closer to the ultra in performance.
If the speculation is wrong and it is an entirely new Arch, then maybe it will be worth it. But I doubt it. nvidia is just trying to get the suckers to buy it so they can have more profits.