Well, I got my mouse today!
I installed it, set up the receiver about a foot away from both teh monitor and the mouse, and loaded up Natural Selection for some testing. I noticed very little (if any) lag from when I moved the mouse to when my crosshair/cursor moved, and have no complaints in that department. My only complaint is that the mouse wheel is incredibly touchy, to the point that it's not reasonable to use it to switch weapons in-game. This also causes the wheel-button to be useless, since in the heat of battle you will end up scrolling like mad instead of just clicking the button. It's not as gamer-friendly as my previous mice, but it feels great, is wireless, and was $20 less than similar Logitechs, so it works for me.
I give this mouse 8 out of 10 stars because the mouse wheel is fabuloush anywhere but in FPS games.