There is nothing like it out there, truly mind blowing.
So, it takes you a little bit to get your bearings and understand how things work if you've never played the first Portal game. But, it's not long before you're shooting holes in walls and manipulating physics.
The story is not terrific but, it's mostly about you trying to escape this underground place and in doing so you travel through a series of puzzles. Your character does not talk, however the other main robotic characters have quite a bit to say over your adventure. Sometimes, this can be annoying as the story is not really good, it's the puzzles that keep you wanting more.
The whole game is not rooms with white walls etc. that you may see in previews. You'll adventure off the beaten path and truly test your eye for minute details and ability to think outside the box. Some parts you'll be stuck on for fifteen minutes and others you'll fly through.
The game does a great job with physics; i.e. you must hit portal A going so fast so that when you come out of portal B you have enough momentum to shoot you across a vast room. When you accomplish such tasks you feel a great sense of well... accomplishment. It's refreshing and neat to find a game that actually makes you think.
You are introduced to many different types of puzzle elements; lasers, bridges, bounce liquid, speed liquid, etc. All of these elements are introduced slowly and at an even pace, so just when think you know everything and it might get boring... bam, there is another twist to how you must solve the puzzle. The puzzles are typically point A to B, you need to reach the other end of the room and leave through a door.
The graphics are very good at points but not great (not Crysis 2), yet it doesn't have to be.... that's not the point. There are no framerate issues of any sort, which is a surprising relief nowadays. The game controls like any other standard FPS, very easy to pick up and start playing.
Overall, Portal 2 was a very refreshing and innovative experience. The only downside is that the story started to drag in the middle parts and perhaps a little short. There is no replay for the main story, but I know PC users can create their own puzzles and share online. Currently, I do not believe PS3 users can participate in this feature, hence crippling and solo replay value.
I have not had a chance to play via split screen, but this seems like another game itself helping add some depth.