I have just moved into a house I remodeled (last May) and during the remodel I replaced all of the heating systems. I would love to have used in-floor radiant heat but couldn't for structural reasons.

What I have is a 3 phase heating system. I use a natural gas insert set on a thermostat in my living room which is central to the house. This pretty much heats 2/3 of the house (1/2 of downstairs, all of upstairs). I have a gas line stubbed into the master bedroom for a small gas stove, but I don't think I will ever install one we will see after this years storm season.

I have a heat pump, the biggest one I could afford which heats down to about 33 degrees, and then an electric furnace for cold temps. It was going last year during that December cold snap. I don't think you need a gas furnace around here, we just do not get that many really cold days where you can't use a heat pump. Our heat bills so far are about half to 2/3 what they were in our prior house which had a small heat pump.

I think that the A/C is nice to have, I only used it a few times last summer, but it comes in handy when you have a large gathering and the house heats up due to all the people in there. You can cool it down really quickly.

The on-demand water heater is awesome. I would highly recommend one of these if you have a busy household. We bought the biggest one they made at the time and mounted it in the attic next to the showers. We have the multiple shower heads in the master shower, and then the kid-bathroom. There is almost no drop off in pressure or heat when all 3 showers and the bathroom sinks are operating on hot. One of the best mechanical items we bought for the house.