The best place for this info is fallout3.wikia.com, which is updated really frequently with new info on the unique weapons (there are a few).
I just started playing it a few hours ago, but then my game crashed (playing the PC version). I've done a few things, but there are a lot more missions than any of the last DLCs. Most people who have played it so far think it's easily the best of the four DLCs. IMO, they have been getting better with each one. 'Anchorage' was really weak, although the weapons you get at end of the simulation were worth it. The Pitt was decent, but I liked all of the new additions with Broken Steel. This one seems a bit weak in the weapons department, but there is a lot to do.