After finally playing Portal 1 (which I had on my account for free due to a promotion a year ago and never playing it) I decided to cave in and buy Portal 2 too. Portal 1 took me like 2 hours, Portal 2 about 7 hours.
Gotta say, the whole thing was great.
I still haven't played Half-Life 2 (or it's episodes) so I probably missed out on a lot of references down in the basement area. Though I did recognise Black Mesa mentioned as stealing their technology.
Just a few of my favourite and/or spoilery bits:
"Oh hi. How are you holding up? Because I'M A POTATO!"
Wheatley was great overall. Oddly I really didn't see the twist coming. Then the very moment your escape lift stops and he's like "Actually....." it was suddenly just like uh oh shoulda saw this coming. Especially liked his not quite articulate enough insults: "Fatty fatty no parents!"
"Holmes vs Moriaty. Aristotle vs MASHY SPIKE PLATE!"
GLaDOS: "This is the part where he kills us."
Wheatley: "Hello! This is the part where I kill you."
CHAPTER 9: THE PART WHERE HE KILLS YOU
Achievement Unlocked: The part where he kills you: This is that part.
Ending spoiler:
What the hell at the MOON! I don't even know why I did that. It was just like, there's the moon, gotta shoot a portal at it, didn't even think about it, nor did I expect it to actually work. Though I have my reservations about how you could actually survive this. You're basically sucked out into space, on the moon, with no kind of suit or anything else. The air pressure alone should probably have instantly killed you, regardless of being 4-5 feet from a portal to Earth's atmosphere.
I'm rather sad about what happens to Wheatley in the end though. I was kinda hoping he'd be back to his normal southern-british silly old self once disconnected from the system. Then seeing him all sorry in space and THEN replacing the main menu with his stuck-in-space self was sad.
Subtle overarching theory spoiler speculation stuff:
So as I understood it: While down stuck in the 70s basement thing, there's a lot of pre-recorded messages from Cave Johnson, the (original) CEO of Aperture Science. And he has a thing for his secretary Caroline.
A rather serious thing because he was prepared to put her in charge of the company once he was gone, if she wasn't his wife, then or eventually, there could have at least been some kind of affair going on there.
In the daycare center, theres a whole bunch of science experiments wired up to potatoes and stuff, and a banner that says "Bring your daughter to work day!". There's also one experiment that's gone completely out of control. If you look closely, that experiment is signed "Chell", you. Additionally, there's a message if you look extremely closely that says "special ingredient from dad's work". This is bring your daugher to work day after all, it seems entirely possible that Cave Johnson is Chell's dad.
In one of the recordings it's revealed that Cave Johnson is sick and dying and has asked the "lab boys" to start coming up with a way to copy himself into an AI. This is around the time he also says to put Caroline, the secretary, in charge if he doesn't live long enough to see them finish inventing it. It's implied that this is what happens, and Caroline is who eventually ends up as an AI -- GLaDOS. This part at least is pretty much fact, it's outright told to you by GLaDOS at the end if you didn't figure it out from the weird responses coming out of your potato.
Dad is CEO Cave Johnson, he's possibly romantically linked to Caroline, the secretary. Caroline is GLaDOS.
Ergo, GLaDOS is actually your mother?