why oh why did i buy this before it went on sale?? well i needed an immediate replacement for my broken mouse, that's why. we all know touchpads are evil.anyways. this baby took a little getting used to. maybe, like another reviewer said, it's ergonomically wrong, but now that i'm used to it, i have no problems with it at all. so maybe it's just me, i was too used to a minimouse and have crazy tiny hands.its functionality is great. i really love the mediaplay buttons, which were the reason i chose this over the MX510 in the first place. be warned though, if you haven't had a mouse with this many programmable buttons before, it's gonna spoil you rotten, so you'd have a hard time using another mouse when you absolutely have to.