bhester,
I use a multiwire circuit (12/3) to the kitchen. One side feeds the countertop outlets on one side of the kitchen, the other feeds the dishwasher disposal (on the same side of the kitchen). Also, I've run a 14/3 to supply two forced air gas furnaces next to each other.
By the by, the only time the code requires a handle tie or common trip breaker is when the two circuits are on the same yoke (like a split outlet). Some inspectors have insisted that I put in a handle tie because the two circuits are in the same box. It is a little safer for some goof who starts poking around in the j-box, and checks only one side of the multiwire...
