When one uninstalls a program, sometimes stuff is left over. I just uninstalled Office 2007 and updated to 2010. The stuff left over from the 2007 version, would that have been written over by 2010? Or would it make new entries in the registry.
I had some bad experiences with Revo few months ago I installed it in an attempt to help me remove Replay Media Catcher (which proved a pain to uninstall). Not only it didn't make it, but afterwards I was also unable to remove Revo as well Surely, I don't think its that bad; it was probably just me been unlucky or the fact that this happened on a Vista installation ...
I use the Windows uninstaller and then scrub the registry with Ccleaner. Leftover folders get deleted before scrubbing the registry. I don't like to combine operations; separate tools afford me more control.