Ditto on MP3 Tag Studio, although I would go insane if all of my MP3s were only named by the song title. Oh well, to each his own.

I just wanted to chime in to recommend another piece of software to anyone who's looking, called The Rename. I am constantly using that program in conjunction with MP3 Tag Studio. It's the most powerful batch file renamer I've come across. Wait, it's the only batch file renamer I've come across. But it's still very powerful!