Meanwhile I agree with Will Baude at Crescat Sententia that most U. Chicago undergrads address faculty as "Professor" rather than say "Mr. Fortnow" as is the official Chicago custom. A decade ago I was more likely to get "Mr. Fortnow" which I never loved since it actually feels more formal than Professor or Doctor.
Graduate students as well as my colleagues call me "Lance," at least to my face. First year grad students sometimes take time to grow out of addressing professors as "Professor." I had this problem myself way back when. A fellow student couldn't shake the professor habit until he started playing sports with them. You just can't say "Throw me the ball, Professor Leighton."
In the end I don't really care that much what you call me. However I do enjoy those letters from Germany that covering all the bases address me as "Herr Dr. Prof. Fortnow."