We were at a Sears Hometown Store today looking at fridges. We specifically asked the salesperson what they did to clean all their appliances. He said plain vinegar and microfiber cloths (they use a clean one to dry the fridge after cleaning).
I've been using a home mixture of vinegar, rubbing alcohol, water and corn starch + lavender oil. It cleans mine like a dream, but I'm not sure if I would be brave enough to test it on a subzero.