Like everyone else is saying, I had this mouse the first day it was released, Used it for about an hour, and put it right back in the box for return. Microsoft really screwed up this one, not sure why. In the past all microsoft mouses have been mega kick ars but I guess they just wanted to get a wireless optical out there to compete with logitech, even if it did stink. The thing responds slower then any mouse I've ever used. STAY AWAY if you like to use mice for computers and not to chase around the house(ok that was lame I admit).