There are many words to describe Limbo, I'll pick one: awesome!
In fact, there is no storyline at all. All that you know is that the boy wakes up in a dark forest, and has to make it's way to the end.
It will not be an easy walkover though: The further you get, the harder it will become. The boy will easily fall victim to a cruel and painful death, and there are many "original" ways the kid can lose his life!
And that is one of the better points of the game: you will feel empathy to the boy, and it is painful and sad to see when the kid drowns in a lake or falls in a pit full of spikes.
Other good points about the game:
+The graphics are absolutely amazing, it's only black and white but with so many details, there is hardly any music in the game, only sound effects, and they're brilliant.
+The game is not too difficult, but absolutely not easy, too. The puzzles are not extremely difficult like they are in Braid, but it will take some time to solve the harder ones. While the boy can only walk and jump, there are some handy attributes in the surroundings to solve the puzzles.
+The atmosphere of the game is absolutely creepy and horrifying! There is one time in the game that made my heart lose a beat. I won't tell you what it was, I don't want spoilers in this review.
There is just one major drawback in the game: It's length. You'll be able to complete the game in under 5 hours. Yes, that's really short. And when you reach the ending, there is little to come back to, only to get some achievements. This also made me question it's price tag: 1200 ms points is a little too much for such a short game. I really hope there will be free downloadable content to make my doubts about this go away.
Lately, I hear a discussion going on if this game is better than Braid. Well, I think they are totally different games: Braid is much harder with more impact to puzzle solving, while Limbo has the weight much more on platforming. So you have to decide for yourself, I would recommend them both.
Nevertheless, if you would like to play an original, challenging platformer, Limbo is surely recommendable. But if you wait until they drop the price to 800 ms points, then Limbo is a must-buy!