Always best to be cautious and only edit your registry as a last resort if you don't know what you're doing.
I assume you have a problem in the first place to think about messing with it?
No, I read somewhere that if you use their general "cleaning" routines it can improve performance of your computer.
Editing your registry can cause major problems with your computer. If there's nothing wrong with it, I would strongly recommend that you don't mess with the registry.