There's no inherent value to a digital thermostat over analog other than precision. If a few degrees either way don't matter - and they won't here - then analog would seem simpler and more efficient.

He never seems to have looked into the insulation properties of his freezer vs. refrigerator. I bet that freezer leaks heat a lot less, and that this accounts for a lot of the efficiency gains.

A neat idea, but it needs a lot of space. I don't have room anywhere indoors for such a thing.