My verdict: If you have to watch Twilight, the RiffTrax commentary is a must. The movie was pretty bad—almost as bad as I expected it to be. The commentary is often hilarious, though it has some profanity and is lewd in a couple of instances. Not surprisingly, there were some scenes that were unintentionally hilarious aside from or even in the absence of the RiffTrax commentary—Edward looking like he was going to throw up when he realized Bella would be his lab partner in biology, Jasper staring ravenously at Bella, the "spider monkey" quote, etc. The only praise I really have for the movie itself is that there was some good cinematography of the Washington rain forest.
 Rifftrax is the successor to Mystery Science Theater 3000 (to read some of my MST3K reviews, see here and here). Rather than record their commentary over the movie (which requires them to purchase distribution rights), now they just record their audio commentary and you play it while watching the movie. You can preview and/or purchase the RiffTrax commentary for Twilight here.
 You can download it for free here. It handles more types of files than either Windows Media Player or iTunes, so I recommend it.
 My opinion of the movie before seeing it was mainly based on previews and other spoofs, e.g. Buffy vs. Edward, How Twilight Should've Ended, and 30-Second Bunny Theater: Twilight. Oh, and don't forget to look at the Kristen Stewart vs. Emma Watson montage.
 We also got to see some rather ridiculous deleted scenes sans commentary.
Twilight in Norway is by Sondrekv, available at http://commons.wikimedia.org/wiki/File:Darkness1.JPG.