You know Griff, I think you're right that using the seat heater and and heated steering wheel in the winter would use less energy than using the heater to warm the entire cabin. Everyone has said the heater really drains the battery. I think hat is the reason the Volt will turn on the heated seats first when you want to warm the cabin - at least that is what I remember reading about the Volt.
Cool breezes on one's buns or warm buns would give the perception that I'm getting cooler or warmer! Where I live if you park the car in the sun during the summer months I doubt that the cooled seats would be enough to stop the sweating. Still, not many entry level luxury cars offer cooled seats and heating steering wheels.
I don't know how often I would use those options but I wouldn't mind the snotty factor to tell my friends, "Look at the options I have!"