Fallout: Brotherhood of Steel is very close to being as good as the Baldur's Gate: Dark Alliance game it is based on (game engine wise). It takes the exact same graphics engine, nearly the exact same control scheme, the exact same loading/saving/menu options and puts them into the world of Fallout, instead of Dungeons and Dragons. This is, largely, a good thing. I'm as big a fan of sword and sorcery as the next guy, but the burnt-out husk of a radiated post-apocalyptic world that is Fallout is a nice change of pace. The talk is brash and dirty as any game I've played, you can sleep with prostitutes and tell politicians to go (screw) themselves using the most colorful languages.
I would say, however, that there are some slight failings. The graphics for some reason don't flow quite as smoothly as they did in BGDA; the combat is also not as perfectly tailored. While you can specialize in melee or guns, the ranged/melee balance found in BGDA just isn't quite as well put-together. The timing of the attacks of enemies isn't quite as progressive, and the acting on the part of the game-engine NPC characters just isn't as vibrant or well animated as it was in BGDA.
That being said, I still enjoy Fallout: Brotherhood a great deal, and recommend it if you're not averse to harsh deeds, harsh language and gross, sticky, mutated dirty worlds. While it's not quite what it could've been, it is a very enjoyable adventure that's worthwhile.