I have no direct experience with them, but I did seriously consider them before purchasing a "conventional" Filon/Aluminum trailer. They are great because you can store them in your garage because they have the folding tongue option and you can tow them with "less powerful" tow vehicles. So I considered one in order to not have to buy a new tow vehicle. I think the miles per gallon argument is not significant, because most people don't tow that many miles anyhow.
The bottom line is I thought the setup was way too much work. I know the Trailmanor salespeople tell you that it can be set up in X amount of minutes-but try doing that in a blinding rainstorm which I have experienced. The beauty of a conventional hard sided trailer is you can just run back there until the storm passes and then set up.
They do keep their resale value, but then again your market to sell it used is pretty narrow. You have to find someone who wants that type of trailer.
Good luck in whatever you decide.