Thanks guys for an excellent program! I have a way that would make it even more useful for people constantly adding to stable collections. The folder grouping feature works great when adding to a collection, but I want to be able to Automark duplicates that are located in a particular Folder Group - say, mark all duplicates that are above 95% precise and in Group #2. This would allow the user to only delete songs from the folder they were trying to add. Right now, unless I'm missing something, there's no way to do this and I have to manually select each duplicate from the folder group I want.
A second option that would help very much sorting through results is a filter/search bar. Are you looking among your duplicates that are just from a particular artist/album? Type it in the search bar and watch your results narrow down to your search! Maybe I just like Google's Instant Search to much...