I think CCleaner is some of the very best Windows software I've ever used and I think Windows isn't complete without it. I love it and really can't picture myself using Windows without it. I've started using Mac OS X lately and although there's no registry to clean and less problems related to trash than on Windows, it would be awesome to have CCleaner available on Mac OS X as well!
So how about it? I would definately pay money for it!