I just finished my second JS10K entry (also a game, but much simpler) in about the same total time (though spread over more days).
I found the hardest part was to balance playability of the game. I played it so many times while developing it that what was easy for me turned out to be very difficult for others.
At least with such short competitions your involvement is limited. Constraints work both ways: deadlines are liberating when they pass.
I'm sure I would do my best to appear attentive when working on something like this, limiting my twitter/facebook/hn browsing to my iPhone/iPod/laptop.
He posted about development progress.
Here's the sound effect program he was using, btw: