I pretty much agree with IanC14. Imaginationland is a fantastic three parter by Matt and Trey, and the version on the DVD is the "Director's Cut" version. I think there might be one or two scene transitions that are longer than the one that was aired, and no swear words are beeped. Also included are two bonus episodes - Woodland Critter Christmas, and Manbearpig.
Anyway, I love South Park, and if you do, you'll have a real hoot watching these episodes, especially if you've never seen them before. Unfortunately, the actual video quality on this DVD isn't that great (same thing with The Cult of Eric Cartman, another South Park DVD). There's lots of combing present (artefact of interlaced video), and there's some weird letterboxed widescreen thing going on.
It's a shame, and is the reason I gave this DVD four stars, otherwise it'd have gotten five. Anyway, it's not too ruinous, and let's face it - South Park looks like crap, anyway. The stuff on the DVD looks as good as it does on television, and for South Park that's good enough, really. It's a shame they didn't make it progressive-scan and such, but it doesn't really matter.