Performance in Synthetic Benchmarks
This is what you could expect to see considering that 3DMark uses a resolution of 1024x768 without FSAA by default. The GeForce 8800 GTS 512MB is only slower than the ATI Radeon HD 3870 and by a very narrow margin, too.
The outcome of the gaming tests run at higher resolutions with 4x FSAA is more true to life. The WinFast PX8800 GTS 512MB is far ahead of the GeForce 8800 GTX at low resolutions but feels limited by its lower memory subsystem performance at higher resolutions. Anyway, the GeForce 8800 GTS 512MB seems to be a worthy successor to the GeForce 8800 GTX.