We have the same 400D unit in our coach. I will tell you, that when we were looking at our coach, my uneducated opinion of Aqua Hot was that it was a highly over priced water heater. Boy, was I wrong! It is safe to say, that we will never own another coach without an Aqua Hot.
The idea of endless hot water is nice, but realistically, neither of us are one to take hour long showers. However, the idea that we are able to have the washer running, while taking a shower and never running out of hot water is great. However, the BEST thing we enjoy about our Aqua Hot is the comfort heat that it produces. The heat is quiet and evenly dispersed throughout the coach. We have been in some very cold areas and found that the unit produces more than enough heat to keep the entire coach comfortable.
Safe travels.