CCleaner's reg cleaner is what I refer to as a non-invasive reg cleaner, it is the only one I fully trust. As for any performance increase I never noticed but because I run it here and there it never has much to clean.
By non-invasive I mean it is not as thorough as some others giving it the best chance not to create errors.
For example I just downloaded a different reg cleaner and straight after running CCleaner's it found an additional 2813 problems. I'm almost tempted to create an image of my system and then clean those entries to see if I get any performance increase.