i use the god father for all my id3 tag needs:
http://users.forthnet.gr/the/jtclipper/
it's the best I've found so far, it can edit tags in mass, and restructure them physicly based off of the tags.
just remember that not all devices can use the id3c2 tags (my car mp3 player is one of them.) so make sure you don't have any legacy devices before you wipe them all