I recently imported a GEDCOM file and ended up with duplicates of every person in my tree, which was realized too late to actually fix it. Now I am left with over 820 duplicate entries, some with more information than the duplicate copy.
Adding on to the duplicate person tool, a feature where you could merge duplicate people would be nice. This way, you wouldn't be left to delete and move people by hand or broke linage, and you could select which information to change/move over/etc.