Just installed the drivers and ran 3DMark2001SE. There was no 1000 point performance jump; my score went up "only" 600 points (from ~8200 to 8760). My framerate for the first 3 tests was almost exactly the same as it was with the previous detonators, but the Nature test ran between 20-40fps faster. I assume the tests with DX8.1 features received the largest boost from the new drivers. Haven't had a chance to try any games, though.
I thought that nvidia's previous drivers were squeezing every last bit of power from my GeForce4, but I guess not. Very impressive to say the least.