Since this is just a technology overview we will not give a score, yet. But even without a score it is evident that the GeForce 8800 series will rock the industry. The performance increase is close to factor two which is a huge leap forward from one generation to another. Even at the rather low core clocks of 500 MHz / 575 MHz the performance is there. If the production process matures, you will see even higher clock speeds. Probably together with a die shrink to a process smaller than 90nm. Right now the huge GPU is very expensive to make.
Since this card is the first Shader Model 4.0 product on the market, competitive performance is yet unknown. Also Microsoft Vista with DirectX 10 is not yet available. Success of DX10 depends largely on whether the gaming industry will (can?) bring out new titles fast enough to drive the demand for these cards.
But even without DirectX 10 it is safe to say that the GeForce 8800 GTX is the fastest DirectX9 card on the planet. While there has been a minor issue with a resistor on the 8800 GTX boards, the GTS boards are unaffected and will be on sale today. Fixing the GTX boards will only take a few days, so expect cards available before the weekend.
Does ATI have anything competitive? No. They are working hard on their R600 based video cards but these will most probably not come out this year. This leaves the whole Christmas business to NVIDIA which may be huge if Vista takes off.