If you currently have duct work for a central AC system then replacing your current condenser with a heat pump is relatively easy. The heat pump equipment is not much more expensive than the similar AC condenser model.

What furnace do you currently have? How much do you pay for propane and what are your electricity rates?

You could set up a dual fuel system with with your propane furnace. In most parts of the country it is cheaper to heat a home with a heat pump than a propane furnace. Heat pumps are as reliable as AC condensers. Their life expectancy may be shorter because they operate in summer and winter.

heat pumps are very reliable. Its more important to go with a better quality one in my opinion since they will be running alot more than a straight a/c. If your in a cold climate and have access to other fuels it might be good to use them during extreme cold snaps for comforts sake.

A heat pumps shouldn't cost much more than the same version A/C unit in many situations unless the contractor is charging extra money for profit. You just need a better thermostat to handle heatpump and propane furnace. You could run the heatpump during milder cold weather like 30 and above and probably save money over the propane and it would be pretty comfy. Heatpumps aren't so good in drafy houses btw.