It seems all the rippers use freedb for the recognition. But freedb doesn't include many extended attributes (like Composer, Studio, etc.) or cover art and it's not always accurate.
My friend just installed Plutohome.org, an open source Linux media project. Whenever he inserts a CD, it recognizes the disc, displays the cover art, along with all the detailed attributes, like a Windows XP Media Center does. It also seems to cache this locally since the next time he puts the disc in the recognition is instant; first time there's a 2 second delay or so. Can this identification engine be used instead of freedb?