Level 12
Registry clean up can help in some cases such as slowdowns in the startup as the computer tries to run software no longer installed or the right click menu making references to old software but it really is the user's choice whether he wants to edit the registry manually or if he wants to use an automated tool. I know many tools out there that do more damage than good.
That's a good point about the right click menu, they can get out hand and need reigning in from time to time.

If I'm being honest, the tool that does more harm than good than any other is probably... Me ;)