Good, not great.
The irony of Limbo is that the artistic design of the game is its greatest strength and greatest weakness.
I appreciate the minimalism. I appreciate the presentation. I even appreciate the mostly well-crafted puzzle design (this is coming from someone who generally dislikes puzzle games). But, once the freshness of the presentation fades, the games flaws begin to come alight. The environment is built in such a way that every step you take could be your last. This creates a kind of wonderful tension to your actions. As the game progresses however, you soon realize that there is actually little you can do to prevent your inevitable demise. The game relies heavily on trial and error gameplay and when there isn't any real consequence for dying, there is no incentive to tread more carefully. And once the tension is gone, the game can get quite boring.
As it turns out, it's pretty brief as well. I finished in under 3 hours - I wouldn't be surprised if people beat it in under 2, first run-through. And, as much as I hate to say it, by about the 2 hour mark I was ready for it to be over. Perhaps the bleakness will speak better to you, but the lack of exposition and music really diminished the experience, as there isn't enough to distinguish one creepy, dark environment from another. And like I said, I respect the minimalism, which carried over into the ending, but it also made it a very forgettable experience. Unless you are the type that feels you need to collect everything (I am certainly not this), then there will be little reason to play through the game again. The $10 price tag looks quite a bit less appealing after completing it in a single night. I didn't dislike my time with Limbo, but I was left wanting.
(P.S. A lot comparisons have been made to other, smaller indie titles like Braid, World of Goo, VVVVVV, Flower, etc. Limbo is not "A Tier" indie.)