The biggest problem with the end is its all so anti-climatic. I dont want to spoil the end, but there isnt much of a challenge to it, and the end video (if you wanna call it that) is pretty lame!
The fact there is no free roam (which you could do in Oblivion), is a bit annoying as well.
Another thing I disliked is the fact that if you are playing the storymode, and have done a lot of the side missions early, you only get to wear power armour for a short time, as it only becomes available to wear, right at the end of the game.
Its definetly got a high replayability factor as everyone I know who is playing it, is having a totally different experience.
I also hope they can come up with some kinda patch for the PS3, as its bugged to fucked.
