Well, back during my FPS days I used 2000 DPS and as I was mainly the sniper, I always played on low sensitivity so I had this 55*60cm mousepad.
Now convert this to Freelancer and you'll get how I play. I don't use that old pad anymore, but I still have to move the mouse around to go from one side of the screen to another, cause even though DPS is 2000, I have the in-game sensitivity at near minimum. Useless in a game like FL, I know, but it's an old habit, so yeah...:P
Fast DPI for shooters, slow for FL. I bought a fancy adjustable mouse two days ago. Switched straight back to my old one because it was to big and affected my aim too much. The buttons I could press with my thumb to drop mines and fire CDs were fun though.