Not that it is useful feature to everyone, but it would help people who want to spend time filling DB with data.
So, suppose I got lots of time to hash some files, I want feature that would check mylist and show me list of all non-deleted files in mylist that don't have some checksum or video/audio data that AoM can calculate, so I can fetch discs with those files and feed them to AoM.
Another similar feature would help people who add japanese/romaji names - list of all anime and eps in mylist that don't have yet romaji and japanese names (with ability to add to inore list those names that are non-japanese from begining).