Beat Portal 2 last night! Much as I enjoyed the first game, Portal 2 blows it out of the water. The world is more expansive, there's more variation, the writing is better, etc. It's like Portal is the tech demo, and Portal 2 is the actual game.
I'm going to agree with many other folks and say that the trek through Old Aperture is the best part of the game. It's the first time you really step outside the claustrophobic confines of the testing facility, and Old Aperture gives you almost the opposite feeling -- it's so huge that it's almost intimidating. Just making your way around that place is an adventure in and of itself.
Also, Portal and its sequel are great examples of how good, smart writing can really amplify the effects of simple stories. Even though Portal 2 has a much expanded storyline, it's still simple at heart, and fairly predictable at that. But the writing is so strong and funny that it makes the story seem like much more than it is.
Honestly, despite the "OMG VIDEO GAMES ARE ART" movement, a lot of video game writing is still barely at potboiler level. But Portal 2 is genuinely strong, clever entertainment, with every aspect -- writing, voice acting, level design, etc. -- not only drawing the player into this world but also creating a real emotional attachment. I mean, I even felt genuinely sorry for Wheatley at the end!
I will say that I'm not totally done with the game yet, though. Still have to go through the co-op portion, which, if what I'm hearing is true, is even better than single player, at least when it comes to the puzzles. Definitely looking forward to it!
