Mutlien pretty much summed up the Fallout DLC. I'm currently on Broken Steel which I do enjoy very much, have not gone onto Point Lookout or Mothership Zeta so can't say anything about them. From what I've heard, Point Lookout is really good but Mothership has recieved some mixed feedback so you'll just have to see it for yourself.
The Pitt was nice although a little bit "meh" in my opinion but not bad in any way. Also loved the "Escape from NY/LA" wibe from it. Operation Anchorage was a bit boring since it is really action oriented and without ironsights it's just a V.A.T.S. fest. But the gear you get as a reward is pretty awesome so it really is worth it.
I highly recommend Deus Ex. It's an awesome game eventhough it has some flaws. Sure it's not for everyone but if you like Metal Gear, you're gonna love DX. I'd recommend buying it cheap and giving it a testdrive, to minimize the losses if it not your cup of tea.