OP here. I posted this elsewhere (
https://news.slashdot.org/comm... ) but I'll provide additional information here as well:
Two years ago I went through the process of quoting out a ground-source heat pump. Total out of pocket cost for Installation was around $40k. Payback took about 16 years, using whole year savings estimated (both heating and A/C). The warranty on the unit was only 10 years, and as mentioned above my neighbors got hit with a $16k repair bill when their unit failed right around the payback point (which extended payback out another 6+ years for them). No one that I have talked to who has one of these things has reported smooth sailing (but take this with a BIG grain of salt, I only know two other families who have them). Hence why I ask the question.
Furnaces cost FAR less than what I've seen of repairs on heat pumps. In my anecdotal experience, furnaces seem to be FAR more reliable, and in the case of a full replacement being needed they're about 1/4 the cost of a heat pump. I love the idea of heat pumps, but they need to make financial sense before people will be able to convert to them in numbers high enough to matter.