We do self-serve popcorn at one location, popcorn is placed in a warmer that has both front and rear entry, the warmer is built into the center of the concession counter.
We have played with all sorts of self-serve scenarios. What works for us, pop, corn, butter/salt, hot dogs, and nachos. What hasn't worked, bulk candy, slush puppies (created a mess every night), coffee/cappuccino (didn't sell more than I think it didn't work).
We are all about efficiency, the quicker the better. I'll have to get the actual #'s and post them from our 6 plex, but through one stop ticket/concession stations and self serve we have saved a tremendous amount of labor costs over the past year.