Supposedly, the 8800gt will outperform the current 640mb and 320mb 8800gts, at a MUCH lower cost. All reports I've seen say its got 112SP's, but none of it is confirmed by nvidia or any of their partners.
Therefore nvidia are releasing a new model of the 8800GTS, with 640mb version only, but with 112SP's. Still 90nm.
Even though they'll both have 112sp's, the GTS has other advantages such as 320bit over 256bit, 640mb of memory over 512mb, and probably more ROP's and texture units.
None of that is confirmed by anyone official, but several different sites have "tested" their cards and come up with similar but different benchmarks results on 3dmark06.
Don't believe anything that puts this card over the GTX/Ultra, it wont beat them. The 8800GTS as it is is being phased out and ceasing production, the 8800gtx is going on though.
Supposedly its going on until a 65nm DUAL 8800gt card comes out next year, a GX2 style card. 8800gt will be closer to a GTX then the 8800gts atm so it'll be a nice improvement over an ultra.
Then again none of that in confirmed
Ill try find some links.