work great apart from the scroll ball thing on top clogging once in a while. i have tried my old favourite MS intellimouse, but it's just so "unapple" it offends my sensibilities
I've had good success with a lint free paper towel and monitor cleaning fluid to rub into the top, then turn it upside down and roll it about fairly vigourously in all directions on another dry one.
Also, less pies at the desk seems to stop it going wonky in the first place. I think it picks up fat/butter/<whatever> and stops tracking in one direction usually.
3 BT ones in use and haven't had them go bad since I broke the food at the computer habit.
I've had good success with a lint free paper towel and monitor cleaning fluid to rub into the top, then turn it upside down and roll it about fairly vigourously in all directions on another dry one.