What kind of settings/mice do you guys use? Most people are shocked when I tell them I use a trackball mouse to play FPS games, but it's true. I find the trackball to be much faster and accurate than a regular mouse. Instead of having to move the entire mouse around, I only have to manipulate the ball, and it can be moved at rapid speed. For a couple months I had to use a regular mouse, and it really made me a poor player; eventuall I got better with it, but I found myself constantly losing battles where someone would attack me from behind and I simply couldn't turn around fast enough. I got my trackball mouse back a couple days ago and I'm kicking ass again.
Also, what about sensitivity? I originally played with mine really high (like 5.15), but now I have it lower (around 3.0). My brother played with a sensitivity of around 1.2 and I don't see how he can do that. o_O