My Dream Tagger
How it would work:
scans designated directories for my music files and maintain a database of MBIDs
(on a schedule) checks for artist updates
if there are artist updates, check release updates
if there are release updates, check which tracks were updated
ask to apply updates
little pop-up from the system tray to notify that there are new updates
"Hey, there's an update for some of your tracks. Would you like to see them now?"
tray shows queue of new updates
click apply to make changes