I just downloaded this yesterday and I must say I have been extremely impressed. In an age where realism is the aim of many games I find it get rather boring to play the same games with different guns and objectives over and over again. The art style in this game is so great and I agree with the above poster that you just have to sit back and take it all in.
The levels are just challenging enough that you will fail many times but generally can find the solution before you decide to rage quit. It is a refreshing change of pace from most games and I am glad that the indie scene has taken off. I recently have played Machinarium and SPAZ (both games I recommend) and Limbo ranks right up there as one of my most favorite experiences in a game so far.
As for the price, I would pay $20 for it so for me, the $10 price point is great. Assuming you get 3-4 hours out of it, that's cheaper than going to a movie. There are quite a few moments in the game where I just sat back and laughed or was wowed. To compare how I feel playing it, for me it is very similar to the experience of Portal (free right now, BTW). The pacing, twists, and almost expectation that you fail and try multiple times to pass a level make it a very enjoyable game. I would highly recommend it.