The Pitt was great. Lots of new raider type armors, although they are kind of derivatives of the stock kinds. A few new pieces of weaponry.
The trogs are challenging, particularly because of the situation and condition you are in when you first encounter them (trying not to spoil).
The storyline is dark, and fits in with the rest of the game really well. There is no clear "right" or "wrong" outcome, as both are disturbing and each side of the argument has its merits. I Thoroughly enjoyed the main quest, and haven't finished some of the side ones yet. The Pitt's design is beautiful and detailed, in a post-apocalyptic way. It isn't really like anything in the stock game. I really liked it.
If you have used any of the multiple companion exploits/glitches, the Pitt will mess that up when you start the quest as they will all be sent home and can't come with you. You can get them all back after the main quest of the Pitt, though.
I am excited about broken steel, as well. Basically, this has been the first game whose DLC has all been worth the price to me. 10 bucks each is good. To think that I will have spent 30 bucks total for all 3 makes me feel like i got a bargain, given how many hours of quality gameplay I have gotten from them, and unique items that also make the stock game that much more cool.