When I sit down at a new machine to clean it up, it's a royal PITA to clean ALL the profiles up, especially at a machine that has more than just one or two users. Often I don't have everyone's passwords, so I have to do it manually, browsing through "Documents and Settings\[username]\Local Settings\Temp/Temp.Int.Files" and "Documents and Settings\[username]\Application Data\Mozilla\[application]\Profiles\[all profiles]\cache" etc. -- IMHO CCleaner would REALLY be much more useful if it supported multi-profile cleanup.
