It also has built-in Musicbrainz and CDDB support, can automatically rename files based on format strings (including directory structure), create playlists, etc. etc. It does have a bit of a learning curve and the UI isn't exactly what you'd call intuitive but you can configure just about anything you can think of.
An example workflow: I like to clear any existing tags and fill in the fields by hand (you can use musicbrainz here but I'm anal about how my tracks get named). Then I just save and hit Rename and all my files are renamed based on the tags and my format string and sorted directly into my collection. If it could fetch album cover art from Amazon and lyrics from LyricWiki it'd be perfect.