Took me just about six hours, but beat it.
That... was one HELL of a ride. And, maybe I missed them, but I didn't see an option for challenge or advanced maps... hopefully, they'll add something like that, though most of the puzzles were tricky enough, I'm still not sure I could repeat the feat if I went right back in. And I know I missed a few of the secrets, so I'll need to go back and find those.
And, of course, co-op awaits, which looks exciting as well.
Ending boss was a much better fight, and the ending scenes had me laughing, more than a few times.
Spoilered discussion, including ending, hidden below.
I'm in space!
My god, I loved those puzzles. I had to go over some of them six or seven times, because I flubbed the sequence, just slightly, but I loved it. Short, but fantastically polished. And I LOVED the introduction sequence. "Okay, trying for manual override of the wall! Here we go!"
I like that we had the opportunity to redeem Glados. Even if it was only for a few minutes. And... the moon. That was amazing. That was *hilarious*. THAT is how you kill a boss, by throwing him to the moon.
And I totally agree on the white gel, Veks, that was incredible. I was sitting there for a good few minutes, trying to figure out what was happening... by the time I finished that one, the entire room was splattered with white. It was awesome.
I'm a little disappointed the new song wasn't anywhere near as catchy as 'Still Alive', and, honestly, the game isn't quite as quotable as the original, but it definitely had some excellent banter between the two villains.
I know I'll have more thoughts, as soon as I post this, but for now, it is way past my usual bedtime, so I am going to get some sleep.
A+ game, though.