Wow, I didn't expect Todd would immediatly go "it was a mistake" when someone brought up Fallout 3's ending. I didn't really mind having it end after "Take It Back!". It was different than what they'd done in the past, but the consequences of the choices you made were bigger.
I liked being able to continue the story in Broken Steel, but it kinda sucked that they just completely ruined the endgame decisions because of it. There never were big choices like that in TES games, though, so it would suck a lot more if we couldn't carry on here. But I didn't really mind in Fallout 3, and I sure don't now in New Vegas.