We have a suburban in our C and an Atwood in our A. We are full timers since the last 10 years and one or the other is on whenever we are in one of the coaches. I had control board go in the Atwood 8 years ago. Has worked flawlessly since. I had an on/off switch go in the suburban about 6 years ago, it has worked flawlessly since.
I have had experience with the various on demand systems in my line of work (seasonally employed in parts, service and sales in the RV world). All were troublesome to some degree and overall customer response has been poor although a few liked them. It would not be something that I would choose at this time.
JMHO