Where I live we put single piece pex tubing in each thermostatically controlled loop and embedded it in a 1.5" layer of concrete. We run a propylene glycol/water mixture, heated by an oil fired furnace. The only problem is that it is still heating the room 24 hours after you shut off the thermostat. But we just set it and forget it. Bedrooms are set cooler than living rooms, bathrooms are set higher so that the air is warm exiting a shower or tub. Once a year I take a sample and try to freeze it in the freezer. If ice forms it needs more antifreeze.
The thermostats are in a row above a manifold which has an adjustable mixing valve feeding it so that in the shoulder seasons the whole living area can be run with less heat. Having had an Aquahot I think it would be a perfect device for the primary heat supply. Overall less maintenance that a traditional furnace and better comfort. You can have it both ways!