I have an MX518 but the concept is the same. I run at 1600dpi and set all my games to match the speed to one that I feel comfortable with at that dpi. I change dpi all the time in game though. Sometimes just to mix it up and sometimes because I'm trying to do something that requires precision like sniping.
For normal computing I have it set at the highest level 2000. In gaming I also have it at 2000, but when I'm playing 2142 I have to set it at the lowest when controlling the tv missiles.