Amazing, if you love exploration and don't particularly care for plot.
However, I felt the main plot was flat out dumb and the ending abrupt and pointless. It's made worse by how exceptional the rest of the game is. Who was put in charge of writing the main story? Fire them. Fire them now. Most games you can tell when the end is getting near, like it's pretty obvious, right? Not Fallout 3. I just wanted to get this boring mission out of the way when BAM! game over. Never did I have any desire to accomplish the main plot, I really only ever did plot related stuff when I had nothing else to do, then the game forced me to stop playing. This ending, while not ruining it for me, could well ruin the whole experience for many people.
As well, the level cap is far, far too low. I reached the maximum level when about halfway through the main story. It's really frustrating when you realize that you straight up cannot get any better. This is it, your character is the best he can be (barring skill books and bobbleheads to give you more skill) and you still have to put up with the rest of the story without so much as a new perk.
Still, everything else in it is so completely and totally awesome that I'd feel terrible giving it any less than a 9. I love this game, don't get me wrong, just the second play through, I'll make sure not to accidentally do the final mission and have my game ended on me.