Should you be contemplating a purchase of Obsidian's initial set of DLC for Fallout: New Vegas, you may want to have a look at our freshly posted Dead Money review to help you make up your mind.
Nicely, Dead Money has a lot of things going for it. Most importantly, at least for me, is that it doesn't play anything like New Vegas or Fallout 3. The action takes place at the Sierra Madre Casino and the villa surrounding it, which has a unique appearance (and possibly even answers the question of what Fallout: Spain might look like), and you have to do odd things like dodge radios and speakers, run through poisonous gas, and defeat enemies by dismembering them or decapitating them (if you don't then they just get right back up and attack you again). Plus, because you lose your equipment, you have to scrounge around for supplies (which are seriously limited, at least for a while), and you have to use items that you're not accustomed to. I bet I ate more pre-war junk food in the DLC than I had with all of my New Vegas and Fallout 3 characters combined.