I didn't know anyone actually inverted the mouse for FPS.
Flight controls, etc. I can understand, but not the actual FPS! When I push the mouse forward I want the damn crosshairs to go UP. I can't imagine doing it the other way. I guess if ya play a lot of console FPS games that use inverted controls (most) then you could get used to playing PC FPS games like that, but using joysticks is way different from using a mouse.
-Lasereth