I'm using the bog standard optical mouse that came with my eMac. I used to use it without a mouse mat, thinking there would be no need for one (optical and what have you...) Anyways, i just found the build up of grime and dust etc to cause the mouse to scratch about, rather than smoothly glide accross the desk. The desk is a laminated wooden type affair, and i keep everything very clean. I have never seen any other mac users using mouse mats, but i wonder how they cope with all the build up of crap under the mouse. Even if it looks perfectly clean (and the dek is wiped down) it can still be scratchy. Is it just me who is affected?