Well this thing has been a long time coming... I've finally commandeered a temperature controller, the company I work for sells them and it took me a while to figure out how to get one for free
Here's a photo of the controller... My only complaint is that it only has a variance of 2 degrees. I currently have it set at 39, so it will kick the compressor on when it warms to 41, then kick off when it hits 39.
The other thing that I'm quite concerned about is that the compressor is running A LOT, or so it seems... I'm sure it will get better when I get a few more kegs in there, but right now it will only kick off for about 15-20 minutes before it cycles back on. I'm not sure what else I can do to help it hold temp. I have a small fan running 24/7 inside to circulate air, and I also have what I think to be pretty decent insulation in the lid.... I removed the factory insulation and replaced it with two 3/4" sheets of R5 foam insulation, and then used the spray foam that expands to fill in the gaps around the edge. I also have about 3/4 of the inside of the collar covered with the same thing. I do not have the probe in water or anything, perhaps I should give that a try?