Ignoring some of the nasty bugs (software bugs, that is), Fallout 3 was a pleasure to play. The graphics were good, lots of interesting characters, and above all a big world to explore as you wish. Developer Bethesda released their first Fallout 3 expansion a few months ago. Operation Anchorage is more of a first person shooter than the hybrid RPG/FPS Fallout 3 is. The Pitt add-on is more similar to the original game. You get to explore Pittsburgh, a city that has not been affected by nuclear fallout as much as the cities in Fallout 3. IGN has posted a review on their site, including video footage. Take a look here.
I’m afraid The Pitt is a bit buggy, hopefully Bethesda will be releasing a patch soon.