Bought if off Steam, and the game kept crashing to desktop. After an hour or two of trying various fixes to no avail, I gave up. Then I found out my friend just bought and completed it on Xbox, so I borrowed it. Just finished it up this afternoon.
I replayed the first Portal while the game was downloading, and as of right now, I honestly thing Portal 2 is better. It's more or less the same gameplay, but then it's like six times longer, and they keep on throwing new elements at you to keep things interesting. It's still not the longest game you'll play, but at least it is a "full" game now. And I haven't even touched the co-op maps yet, which I hear is pretty good times. Due to the length, a couple parts did drag on a little bit, but that was usually about one test chamber before something new or interesting happened, so I guess the timing works out pretty well. As an added bonus, a number of the later puzzles are actually challenging. Occasionally it's for stupid "I don't know where the fuck I'm supposed to be going" reasons, but more often there's legitimate difficulty that necessitates a few minutes of dicking around to figure out what to do.
Dialogue was one of the best things about the first Portal, and I honestly think they managed to top it. Most of the things that come out of Wheatley and Cave Johnson's mouths (speakers?) are pure gold. And GLaDOS is still GLaDOS, and that's a pretty difficult thing to dislike. Even better, they pulled it off more or less without resorting any of the old jokes. Impressive. All in all, it's a damn funny game. If the opening sequence doesn't make you at least smile, I posit that you are a soulless shell of a human being.
My favorite thing, though, has to be all the extra shit they put in for people like me that like trying stupid things. Lots of fun achievements and extra dialogue to be had. And given how much I managed to find by randomly stumbling about, I really want to play through it again and see what else I can dig up.
Here's some shit I found. Mildly spoilerific, maybe? Better safe than sorry
Rescue that poor turret from the "Turret Redemption Chamber?" That's an achievement. Stand in the master turret scanner for shits and giggles? That's an achievement. Try to get into the old vitrified test chambers? Bonus dialogue. Try to piss off Wheately by failing that easy test chamber on the second run through? Amusing dialogue. Actually following Wheatley's instructions after avoiding crushification? Hilarious dialogue. And I'm guessing there pretty much has to be something for breaking GLaDOS' rules and trying to sneak something out of the test chamber with the broken Material Emancipation Grid.
That was longer than I was planning, but hey, I really enjoyed the game. Cut me some slack.