Overly complex and fragile in the long run, the savings are meaningless if you're already self sufficient. I'd much rather spend the money in insulation and self sufficiency than these voodoo appliances.
That's my reasoning my new build house with plenty of land. In other scenarios it might be more beneficial to go for them.
Heatpumps are a proven technology, have been in use for more than a hundred years, and are one of the most efficient (and thereby cost-effective) ways to manage heat.
They're also technically simpler and have fewer components that can wear out. And they're a single system that works both for cooling and heating, rather than needing multiple system investments.
The majority of experts believe that its the future technology stack to manage heat, not a gimmick at all.
That having been said, always start with good insulation first.
It all comes down to building techniques, insulation, airtightness, eliminating thermal bridges, &c. There are also many low tech solutions for heating/cooling, such as air/air heat exchanger couples with ground/water or ground/air heat exchanger at a fraction of the price and a fraction of the maintenance.
Of course the average american living in a mcmansion which wouldn't pass regulations in 1992 Poland cannot use such solutions, but really it isn't a problem of climate, you'll find passive houses from africa to norway and everywhere in between, most of them without heat pumps