I recently took the Moshi cover off my MacBook Pro trackpad after having it installed for about a year. It left a crapload of residue behind. Because I didn't want to use anything harsher than slightly soapy water to clean my trackpad, it took days before enough of the gunk was gone for my trackpad to be fully usable. Even now, a few weeks after removal, there's still some residue on the bottom of the trackpad near the button.