i have the intellimouse explorer, and the only thing i've noticed is sometimes when playing an FPS game, i'll jerk the mouse and my character will end up just staring at the ground running around in circles. all i have to do is pick the mouse up off the surface, and it werks like a charm again. seemed to have a lot more problems when i used win98 and the earlier intellipoint drivers, but the newest ones from M$ seem to be doing better.