Hopefully a lot of people get this so my walkthrough will be bumped in views a bit 8) =P haha.
But really, this is the ONLY game I will ever recommend that you NOT play for the length. It's perfect in how it is. The style is amazing. The ambient setting is beautiful. While I'll probably be on the minority side, I definitely went back to Limbo much more than any other game XBLA game this year besides Meat Boy. But with that said. Limbo is in my top 5 for the year, Meat Boy isn't in my 10.
If you want an awesome, satisfying, and different feel of a game, get it. If it really REALLY matters about how much you get out of the game in terms of length then yes, pass. But if you tend to think like that, you may not like this game at all.
Edit: My only gripe was the price. But being that I had to review it, had it come out at 800msp at the time, it would've been a perfect 10. Which, to me, means a lot. I pick at every game I love. RE4 was the only one worthy to me of that number.