Most of the others are new areas you can call "home", depending on your character's alignment and class. Vile Lair is for evil characters (even better if you are a vampire). Mehrune's Razor is a big dungeon, with a cool evil weapon at the bottom. The Orrey is a minor quest that ends up activating part of the Magic Guild's tower that can grant any character class new abilities.
If you still play the game at all, I'd say they are all worth the new low price.
Long live the console war! Buy 'em all! Just don't give Sony any of your Personal info!