I wanted to share our experience with our previous Aqua-Hot. I always heard to have them serviced yearly. After two years of doing that, I noticed that the nozzle looked brand new. So, we switched to service every other year (and all was fine).
The ability of the service provider can vary. The third time that I had the unit serviced, it was done by an apparently top notch guy. I never had the Aqua Hot run so smooth and smell free.
Yes, as with any system that has an exhaust, there will be a faint smell. Only if we were smack dab up against our neighbors would I not use it. Otherwise, a little distance between units would not be an issue.
We now have a Webasto unit that has a 20 gallon water tank incorporated. We have a tank-less water heater for the shower. It works very similar to the AH unit but shares the antifreeze with the engine. The AH uses a boiler fluid.
MM.