I have to say that this is IMHO the best application out there for tagging serious amounts of mp3s. I've done over 1,200 full albums with it now, and can't say that I've ever found anything better. For the record, I have no affiliation what so ever with the company who produces this software

In regards to having to do one album at a time, this isn't true. You can change the view to list the contents of all subfolders. Then, you can select which songs from which albums you wish to label as what.

Unfortunately, I still have not found a reliable source for category information for mp3 tags. I end up just choosing myself which category is appropriate. With Tag&Rename though, it's very quick to re-tag a few files, an album, or even dozens of albums.