A fun distraction from New Vegas style gameplay
Dead Money is a long DLC (10+ hours) which you must complete in order to get back to the New Vegas map. It's refreshing because it's relatively slow-paced in comparison to the main game, and because you will have to think a bit as well. You will have to take the game slowly, because there are traps which can hurt you, and many that trigger timers that will instantly kill you after about 10 seconds if you cannot find and disable them.
For this reason, I would not play this dlc unless you are getting bored of the main plot. It takes a significant time investment to finish, and if you are still craving to play the main game, this will surely make Dead Money frustrating.
I would also not play this game until you get certain skills buffed (assuming you are a completionist, and want to finish the three new companion 'plots' you will receive with this DLC). I suggest getting Medicine to at least 70, Speech should be high, Repair should be 100 or at least close to it, Explosives should be 30, and Electronics should be high enough to hack most computers. A high Sneak skill would be useful to get the critical bonuses on damage, but it's definitely not crucial. I can't exactly remember which other skills are important, but I wouldn't worry too much, as you can always use the console to add skill magazines, which will buff your character +10(or +20 with the perk) temporarily.
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I thoroughly enjoyed this DLC, and am surprised the user score here is so low. I think that 6.2 average reflects more the fact that players went into the DLC with different expectations, rather than on the quality of the product.