The g92 GTS has the same number of shaders as the GTX, runs faster and uses less power. The only advantage the gtx and ultra have right now is their memory bandwidth and memory size. And this only factors in at high AA and resolutions. I rarely if ever bother with AA so it wont bother me.
AA is actually very important, go play TF2 with no AA and then go play it with max AA and theres a HUGE differance in visual quality. The only game in fact that looks decent with no AA is Crysis and thats cause less then 1% of computers can even run that game with any amount of AA without taking a ridiculous performance hit.