Like David, I enjoy the versatility of choice that our heat pumps offer. When I've already paid for park power, why should I use my diesel to fuel the HydroHot? I can use the electric element of the HHot, but what we've found is that the floor outlet (exchanger) fans are friggin' noisy, and interfere with evening TV. Comfortable conversations in the living area with visitors or ourselves is less than great. There are quieter versions of exchanger fans available, but I've never found enough impetus to shell out for replacements.
We used to have a propane furnace on our old Pace Arrow, but quite often when I paid for park power I used the heat strip in the one roof air to heat the coach. It wasn't at that time a super great heat source, but I easily installed it myself and it sufficed to save some propane when things were cool outside but not freezing. It wasn't quite the same as today's actual heat pumps though.
In our Beaver, by kibashing the HHot thermostat up front and turning on the rear AConditioner's heat pump side, and partially closing the bedroom door or (on our particular floor plan) swinging open the bathroom door to block some AC sound, annoying noise is mitigated up front. In moderate ambient outdoor temps, enough heat gets through the ceiling ports up front to keep things comfortable, rather than expecting the rear floor registers and HHot electric to leach enough heat up to the front. The hitch is that heat pumps only work down to a certain ambient temperature, at which point they cannot extract heat from outside air. After that, you must revert to hydronic floor heat.
Generally, an AC heat pump will cease trying to extract heat at 30 degrees F. Modern DuoTherm thermostat controls will automatically switch at that point to hydronic heat - "Aux Heat" on the control display. When outside temps return to about 42 degrees F, the AC heat pump is automatically turned back on. This automation of course can only occur if you leave the hydronic unit on in either diesel or electric mode so that hot boiler fluid is available to the floor exchangers.
Also be aware that within that 30 to 42 degree range, every 40 minutes the device will go through about a 5 minute defrost cycle, and then resume operation.
Joel