I have 3/4 of the max sensitivity, a 200 (yes, two-hundred) dpi mouse, and a MacBook. You don't need good fps to make a shot, you just need to play the game so much that you know where you are without looking at the screen.
Really, though, it's all about feelin'-it. If you play enough, the shots start coming effortlessly, and you only need to see that moving flash of color in the corner to make a twitch-shot. The Quake pros are experts at that, look at it on Youtube.