I used to notice an odd drift with my mouse at high DPIs. Back when I was still testing different settings I was using a really high DPI (I think it was around 1300-1600), and I noticed that when I would move the mouse quickly, such as while doing a spinner, it would actually have a small drift in tracking to the left. It was very strange. I would start out with the mouse on the center of my pad, but after two or three spinners it would be just about on the edge of the pad on the left. I really couldn't explain it except that the tracking must be faulty when the DPI is set high. The movements probably just don't get picked up very well when the speed picks up. At lower DPI (800), I have not noticed this problem, however. It might just be because any drift is too small to really feel until much movement has been expended.