Mp3tag is alright.
Tag Frontend w/Tag I've used for years. The only thing though before committing to the changes Tag makes
you'd best damn sure use the Test mode option to see what the changes will be first otherwise someone's gonna be pissed! If you do decide on using Tag I can post my configuration files which are full of different ways that files could be named, tagged, etc., it beats building them from scratch, and the tagging configuration file is pre-configured for most audio formats.
I'd suggest Mp3tag as rridgely did, it's periodically updated, and it has a GUI which shows everything that's about to happen plus it can mass tag and rename files.
Also don't forget
Foobar2000 Audio Player is also capable of mass tagging and renaming files too, along with fixing MP3's, and applying or removing
Replaygain.