Mine's at 40 F but I think it is actually lower than that since it is in my garage and it was 3 F last night. I'm acutally getting new garage doors put on this week ( R14 rated ) so hopefully I won't have to move the kegerator into the basement for the winter months.
I also noticed that when it gets coldd, the silicone sealer that I used on my collar does not stick any more, so the collar slides around.