It comes with a Musicbrainz plugin which allows you to select an album in your library and search for it on musicbrainz (e.g. by artist name and year or number of tracks-- so you really dont need to have much info) and then you can select a match (there are usually many releases of a given album and it will actually differentiate between them) and then tag your album with the musicbrainz tags.
In fact you don't even need to use quodlibet to get this feature. It has a separate tagging component called "ex falso" which you can run standalone and then use the player of your choice.
But I would strongly recommend Quodlibet for its organizational capabilities as well. For example it uses special internal tags (not id3 but stored in a separate db) that allow you to associate "people" and "performers" to a track so that the track will appear when you search for any of those people.
Also there are sort tags that allow you to customize where stuff shows up, e.g. I can have a track with Artist tag "London Symphony Orchestra", composer tag "Ludwig von Beethoven" (the proper ID3 tags) BUT I give it the artistsort tag "Beethoven" so it shows up under B. Perfect!
See https://code.google.com/p/quodlibet/wiki/AudioTags or more info.
Lastly it has regex search! And you can make "saved searhes" e.g. playlists. And it's lightweight and has an uncluttered (but highly customizable) interface. And it's very easy to write plugins for it.