I have one of the digital Ranco controllers with a differential that can be set between 1 and 5 degrees. I keep mine at a two degree differential with the set point at 38 degrees and as of two days ago my probe has been in the gel.
Without spending time to log temperatures on a certain interval I can't be sure that it is any more effective than before. Just as a quick observation, it does seem that every time I go in there, the temperature is at 38 degrees. As far as exposed tubing outside the keezer, I have less than one foot.
Additionally I have noticed nothing different in regards to ice formation or moisture. It's about the same (not much, but I need to get some damp rid).
As I said, I think the only way to validate this data would be if I had the time to keep a log every couple of hours or so. I do know that things will probably be different in the summer. Right now the ambient temperature in my garage (depending on whether or not the heater is on in there) varies between 55-70 degrees. In the summer I anticipate it will be a lot warmer. (70-80 degrees plus depending on outdoor temperature). I have no problem heating my garage, but cooling it will be a different animal.
I do know that I am going to put a fan in there. Even with 10' lines I've noticed way more foam in my beer than when it was in the refrigerator. I think the temperature differential between the top and the bottom makes a big difference.