> They are WAY more complex to plan, install and maintain than traditional heating.

I'm curious what about them would be more difficult to plan, install, and maintain. Obviously there are many things to consider when retrofitting a building with a central gas furnace... but otherwise why would they be much more complicated than an air conditioning system?

I've had a lot of mold problems with mine. Because they have to be strong enough to handle the coldest winter days, which makes them way overpowered when running air-conditioning in the summer, which means that when you run them in energy efficient mode, they are actively cooling only a small fraction of the time and all of the condensed water just sits there growing mold all day long. It also leaves the home far more humid than usual because it's not removing nearly as much humidity from the air as a less powerful unit running constantly would.

This isn't a problem with regular air-conditioning that is provisioned correctly for the size of your home, because it winds up actively running a lot of the time so the water is draining as new humidity condenses.