Actually, the 6.47's run very well on my GeForce 256. I was using 5.33 for a long time, and they are a good stable driver, but lack the smoothness and speed of 6.47 IMO.
I primarily play Ultima 9 Ascension in D3D mode, and the 6.47's (plus DirectX 8) made a HUGE difference in rendering performance to the game. This carries more weight with me than 3D Mark scores, since any D3D driver that can render U9 fast has to be very well written indeed...
Regards
Greg