my views on ANY registry cleaner are pretty much expressed in post 14.....it's not that I dislike them, it's more along the lines that automated processes can quite easily accidentally delete keys or modify strings that are not meant to be modified/deleted.
That's just my opinion, though....I have had to fix quite a few pc's that were cratered due to registry 'cleaners', so I have a pretty heathly distrust of them.
As the registry is a fairly sensitive place, and it doesn't really matter if you have dead keys in there (as I mentioned, I've got a 10 year old box that has had more apps loaded onto it than I care to remember, and I've never even cleaned out the crap out of there that has been removed), I've found the best practice is to use something like ntregopt, which just compresses the registry (sort of like defragging your hd), and thereby decreases the boot time.
Again, just my nickel's worth.