@Bi-Polar Bear,
I have never, in all the many years I've spent on computers, felt the need for a registry cleaner. Not once. I've tried them many times too, they removed some stray entries and all that weren't doing anything anyway for the most part. In that sense I think it closely resembles a scam, to sell a product whose need is generated in its own marketing.
If you have a need for registry cleaning, I think you might as well do a clean sweep with a fresh install because you may have other problems that registry cleaning won't do.
Note: I have, however, often found registry changes useful (for which I just use native windows registry editing), to make tweaks, but never a general-purpose registry cleanup tool.
So I second
jgweed, the potential benefits are outweighed by the disadvantages.