We lease, so we have no control over the fact that our thermostat is on the first floor very close to an output vent, no thermostat on the second floor, and inefficient air flow out of first floor vents. Property manager did send an HVAC guy out and confirmed there's not enough air blowing on the first floor, but short of ripping open the ceiling to look for pinched off ductwork ,because everything accessible is functioning fine, there's nothing we can do until we move. The house is less than 10 years old, and it was probably like this from Day 1 due to shoddy contractor work.
So, as a rule, in the winter it gets HOT HOT HOT upstairs and stays so cold on the first floor that my hands and nose feel like ice. And, due to the location of the thermostat (which is very close to the only output vent on 1st floor that flows properly) thinks it's hotter downstairs than it really is and shuts off before it's comfortable temps).
I feel I'm throwing $$ away each month to make it bearable in the living area, so to offset the inefficiency, I turn the central air/heat off unless it's below 65 or above 80 in the house.
I must say it's still a LOT cheaper than what we were paying when we lived in NJ to heat our 50-year old house, but it still stinks when you know you are paying more for utilities than you should have to.
NOTE: I hear many people talking about using space heaters, but I find them to be impractical with (1) a toddler in the house who will stick his fingers and/or "stuff" in them which makes them dangerous, and (2) many models use INCREDIBLE amounts of energy and probably cost more in electricity to run than it would to crank up the central heat another degree or two.