Playing it right now and it's so good, I'm trying to go slow so it won't end quickly
I love the voice acting, probably even more than the superb graphics (especially the lighting effects and shaders) and the gameplay we all know and love.
Really liked the part where Glados says (really minor spoiler), "You're test results came back. It says that you are a horrible person. Really. That's what it says. A horrible person." (/spoiler)
Oh, and one more thing. Join my Facebook group
I always turn around when I get on the elevator in Portal