I tend to keep mine at 43-45 F, but it may also depend on the type of beer you are putting into it. British style ales may be a bit warmer. American lagers and lawnmower beers will be a bit cooler.
how do you have your probe placed in the freezer? is it in a bottle of water? or just hanging in the air? Someone suggested to me that it needs a thermal mass in order to keep the temperature more stable. I just wanted some input from the community.