Incredibly good but sadly too short. The multiplayer with a friend is sooooo funny.
In Portal 2 you simply follow the same storyline adding new characters and the story has a lot of sarcastic humor and a story that keeps you playing till the end. Not the best story I've seen but a good one indeed.
Graphics are amazing, Puzzles are time consuming and mind blowing. A lot of "scientific" artifacts aid you in the quest for survival. Man, what would I do with such elements in real life?
For the multiplayer it's best to play with friends and keep a conversation open so you can discuss the best ideas and strategies together while keeping Glados busy giving you ideas... always share with your friend what you have just heard and let your friend listen to what Glados or anyone says.
Rent it or buy it, simply don't miss it. It's too short but it's worth it's price. Promise!