i agree with you about the ending it was disastrous and so sloppy, i mean i could see they were going for a fable like effect but they did not pull it off at all and it kinda ruined the entire climax, not to mention that it felt forced. i also follow you completely on the ridiculous difficulty(or rather the lack of if you are evil that is) although i would criticize the karma system of being the same drivel as all the other "choice" games in fact i think kotor 2 had a better "choice" system but then again i would defend that game even if god, satan, george lucas and my dog told me that it was a bad game.
basically the choice was still goodie tu shoes or bad ass, although the game did make it feel more real, it made your character's choices seem authentic and morally unique, but it was still the same two bland choices.
however i liked the game because of it's atmosphere that is where the true art of fallout 3 comes out, just the shear magnitude of melancholy and loneliness was awesome, also having followers worked rather well, even though the tactical commands were some of the most basic.