I loved Fallout 3 when I played through it late last year, and so when I heard about the new DLC based out of Pittsburgh I was immediately interested.  Having completed The Pitt I have to say the 800 MS points (~$10) I invested in the game were well worth it.  As its own bite-sized chunk of Fallout 3 this DLC delivers, and the best part is that you don't have to have completed the original game in order to access the content.

The Pitt is much more grimy, gloomy and lurid than the Capital Wasteland.  This DLC is based on a scenario where the same nuclear fallout experienced in D.C. led to bosses in Pittsburgh reactivating the steel mills in order to produce weapons and other goods.  In doing so they essentially close off The Pitt (as it's referred to by its citizens in the game) from outside contact and enslave its populace to do the dirty work.  In such a dire and grotesque situation a plague quickly begins to spread, leaving many of the citizens mutated by radiation, leaving their chances of survival low.  That's where you come in: your objective is to find the cure that the bosses are keeping hidden and free the slaves of The Pitt.  Or don't.

The Pitt - Fallout 3 downloadable content

The choices you make in The Pitt are much more ambiguous than those found in the Capital Wasteland.  Without spoiling anything I can say that there are a few times throughout where the line between good and bad gets pretty fuzzy, but that's part of the fun of the game.  As mentioned above, The Pitt is just a bite-sized chunk when compared to Fallout 3 proper, so there are really only 4-5 hours of gameplay all told.  Still, given that there are a decent amount of new areas to explore and the new weapons and missions are fun I'd have to recommend it, especially if you liked Fallout 3.