I hate timed action and doing this once at the very end of the game really sucked!
I can enjoy games that are 'been there, done that'. Much like Lara Croft and the Guardian of Light, Portal 2 was all about puzzles that in this case you are are forced to work out. The NPC personalities were great but is so often the case the story gets lost and/or in this case there is none to speak of. In fact it gets very complicated to figure out what the story was all about.
Still, I highly recommend this game even though I refuse to give it a real high rating--I suspect I am about the only gamer who vocally dislikes timed action sequences so much.