You've got a pretty cool setup. I considered using an arduino to control my cheese cave, as well, but decided to see if I could just trick a window a/c unit first. Since I was able to do that, I've stuck with it. I'll have to move at some point, and leave the cave behind. At that point, I will probably do something similar to what you've done. I particularly like the idea of being able to program in specific temperature profiles I'd like to follow. Not sure how much utility that will ever actually have, but I like the idea.
I mentioned this in another post, but I'll put it here for your consumption, as well. If you fill your cave with bottles of water (or some other thermal mass), you shouldn't need the 10 minute minimum compressor rest constraint. The compressor will run for longer periods of time (which is actually better for efficiency) because it has so much thermal mass to cool. It will, however, also rest for longer periods of time because there is so much more mass to absorb the energy that causes the temperature to raise. This will lead to slower temperature rise and drop. I'm not sure how this affects affinage, but I presume slowly changing temperatures within a given range are better than rapidly varying temperatures within the same range.