Although removing icons from the desktop doesn't really increase speed or performance of the computer (it's better to prevent their associated programs from unnecessarily running in the background), I still clean things up just to make the desktop look better. I remove them entirely. In addition, since the icons are indeed "unused", the user will only need to access the program occasionally. Occasional access can be made by using the Start Menu or by opening the file from the folder it is placed in..

I've got some users that have NO icons on their desktop because they find accessing files is easier from the Quicklaunch bar or from the Start Menu.. Each to their own.

Hope this helps.