I've only bought 3 of them so far; Broken Steel, Point Lookout, and The Pitt.
Broken Steel gets an automatic 'A' just for unlocking the end of the game and raising the level cap. It added some cool enemies too, like the Ghoul Reavers, and the Supermutant Overlords. The missions are ok, but I didn't find them overly challenging.
Am enjoying Point Lookout so far, although I've only done the first mission (helping Desmond defend the mansion), and have been spending most of my time exploring and killing mutant rednecks, which is fun in and of itself.
Not started The Pitt yet, will probably wait until I've finished Point Lookout first.
wasn't that good for me, I have to say, just not my kind of thing, it felt a bit claustrophobic at times and a bit messy.
I really liked Mothership Zeta
, though, even if it wasn't very challenging as far as gameplay goes. It was a nice change of pace and location and just generally geekily cool.
MZ will be the next one I pick up. I've held off on buying Operation Anchorage, mostly because it (apparently) doesn't add anything to the world, with it being a simulation.
I completed a bit more of PL last night. Did the Tonic mission for Marguerite, which wan't too difficult cause I already had most of the ingerdients. Then I went to the Coastal Grotto, and took part in Plik's safari. That was pretty easy, really. I just placed frag mines all over the place before pressing the signal button, so the first 7 or 8 ghouls didn't even get anywhere near me. Then I used the Lever Rifle and targeted heads in VATS for the rest. The 5% extra damage against ghouls that I got for reading Plik's diary should come in handy, though.