I must disagree with the previous comment about "Nothing more than the user wishes to delete" This is a very wrong statement. As I was perusing the binary around the Firefox cleaning section, I noticed the use of what I would guess is a wildcard to clean out the Firefox history, rather than cleaning just the history, it could accidentally delete other files depending on how in-depth the user is in customization of Firefox.

I would always be careful about knowing exactly what's being cleaned, so I guess it all boils down to trust, and I don't trust an application written in BASIC (realbasic) to clean my computer.