Are registry cleaners any good?

What program to use to clean a registry is like people having their own recipe. What works for some doesn't work for others. How do you know? Some say stay away from free downloads, some swear by them. I just want to get that "Pep" back to my system. Had it for 4 years. Other than being a little sluggish, all is fine. I do regular Virus & Spyware scans. Never touched the registry. Does anyone have any ideas? They would be deeply appreciated. Thanks...