If you were surprised when you 30 Rock won the Emmy for best comedy, it's probably because you've never watched it.
While the viewership is small, 30 Rock is a great show. It's some of the smartest comedy on TV today, with layers and layers of comedy. Since getting the DVDs, I've easily watched each episode at least 5 times, catching something new each time.
The show is focused around the production of a comedy show, like SNL, but focuses almost entirely on the dynamics behind it. Tina Fey, Alec Baldwin, and Tracy Morgan get top-billing, but everyone on the show is hilarious, and it has great depth.
The DVD content is enjoyable. On the 3rd disk, there is some special content, including audio commentary, deleted scenes, and behind the scene footage.
I do, however, have a complaint, touched on by the other reviewer. First, the episodes aren't divided into chapters. It would have been easy and very convenient to split them even at commercial breaks, but instead, there's some hunting involved in episodes. Also, instead of putting separate audio tracks on the episodes, all audio commentary is on the 3rd disk with its own video as well.
All in all, it's absolutely worth it. If you're not into 30 Rock, you need to, and what better way then watching all of the first season.