We managed to get hold of some official benchmarks of the default clocked Geforce 8600 GTS. It scores around 5500 in 3DMark06 at default settings. We are talking about a Core 2 Duo Extreme system with 2GB of memory.
Compared to a GeForce 7600 GT, the new DX10 GeForce 8600 GTS card is significantly faster in games, especially without any filtering turned on. The difference is narrowed down when you enable filtering due to the 128 bit memory interface.