I have a tendency to change the angle of my wrist while I'm playing, causing my mouse to rotate slightly. This causes my mouse to drift away from its starting position as I play, making it more difficult to play long songs without breaks. It's not much of a bother after getting a mouse with no acceleration though, my DeathAdder would actually fall off my mousepad if I didn't re-adjust during breaks (which is unbelievable, considering my mousepad measures 45cm across).