I don't usually have speakers or a headset hooked up into my computer, so I can't hear any of the audio in Limbo. Is the sound an important part of the game from a gameplay perspective? Is it essential to be able to hear it in order to win the game, or is its only purpose to provide atmosphere to the game?
If I recall correctly, the final batch of puzzles basically relies on an audio cue. Beyond that absolute, there are a good set that have you fumbling through the dark where the audio serves to clue you into what's happening/what's coming.
And as mentioned, the audio is a big part of the experience. The game's still good without it, but stellar with.