Man, this is one of those rare games that I just absolutely loved every second of. The story and environment was way more creative that I expected, and I had high expectations coming in. The few characters that exist are all lovable in their own way, and you feel a rare connection to them that doesnt happen in virtually any other game. Very few games can make me laugh out loud, and trying to explain to my wife what was going on in the story made me realize how ridiculous and awesome it all is. The very, very end was just brilliant, even if the last fight itself wasnt as creative as I'd hoped.
How rare is it to find a game with pretty much exactly zero filler? Where the meat of the game is just drenched in fine detail, the way the world feels alive. The physics and the way the levels get crushed at times was really impressive.
And the puzzles themselves were pure perfection. The solution is always there to be figured out, never a cheap trick, but never obvious from the start. Definitely a huge step up from the relatively simple puzzles of the first, and I'm also glad they almost entirely removed the dexterity tests that required fast reaction. Those were never particularly fun puzzles, these are all of the more mental variety. I'm sure they playtested the hell out of them.
I am a bit sad to see there isnt too much in the way of the really tough end-game challenges that were in the XBLA portal, but I'm hoping there will be some good DLC.
Still, thats the only little complaint I can make. Overall, its a masterpiece. Loved it from start to finish, although you MUST play portal 1 before getting into it.