Ya with my system as well it's smooth as silk. Makes you wonder about Quake3 or GL for that matter... Hmmm if you can do this level of Gfx with D3D... why bother with GL? different engine, I know, but still.
Only complaint I have is as FastM has sort of mentioned. Creative Labs is clearly the card they want you to use and also follows under the recommended system requirements for the game. I think thats pure sh_t. There should be equal support of the existing sound cards. I sincerely doubt they tested this game with a Hercules or Turtlebeach card.
But either way, with Audigy I lag, with Hercules I'm smooth as hell.