We have a Precisiontemp RV500 in our '65 Caravel
. Works well whether hooked up to city water and electric, or boondocking hooked to nothing. Uses some water to get started. If that's a problem when boondocking, just collect it and put it back in the tank.
It never makes a sound except for hearing the flame light at start-up. No more "hurricane in the middle of the night". Uses far less propane than a standard water heater, as it only heats what you use, and only heats it once.
It was in the trailer when we bought it. If it ever takes the big dump, I probably would not spend the money to buy another, but we sure enjoy it now.