Once you have a coach with an AquaHot, you'll never go back. As others have stated, periodic maintenance is required, but not overly costly. As the owner, your primary duty is to monitor the coolant level and ensure the unit is properly filled. I have not added more than a quart of coolant in 3 years.
If your coach will sit un-used for the winter, it is critical that the AH be PROPERLY winterized. If the coils freeze and burst, there is no fix. A new $10,000 unit will be your only option. The electronic control box is a component that can fail. Easy to replace yourself, but somewhat expensive (over $700). I had one fail the first year I had the coach.
Like anything else, the more you use it, the better it'll stay running. Letting it sit for months at a time can result in pumps and check valves sticking. Sometimes this can be fixed by simply rapping on them.
AquaHot has all the documentation available online for troubleshooting, maintenance and winterizing, so check that out to learn more.