Whats particularly good about the album is getting hold of tracks that you would have missed other wise, stuff like the Scientist/Dub influenced "Dracula" is a great addition, with its heavy bass sound, and the mellow hip-hopp of "The Sounder".
This is a must have album for the Gorillaz completist (if there is such a thing) but if you have enjoyed even just one of their tracks, its worth picking this up to sample some of their other flavours.