I got 12-14 behind my V8 tundra pulling a 22' hi-lo towlite. The up mechanism is fairly simple though does require maintenance in the form of keeping the cables sprayed with wd-40. The pumps stopped being made awhile ago and I'm not sure if the new hi-lo company is building parts for the old trailers. The 2 piece door got old and so did dust coming in through the seams whether the top was up or down. The air conditioner must be unplugged before dropping the top as well as clearing most everything from the counters.
On the upside, mpg was good for such a large (relatively for me) living space. The quality of the cabinetry and fit/finish was very good. Appliances were all middle of the road which I mean in a good way. They worked well, were reliable, and weren't cheap.
I enjoyed my towlite, and I enjoyed selling it. If mpg was a greater concern, I might have kept the trailer however I didn't like the extra steps of raising the top and using the two piece door. I went back to a stick built conventional trailer, a lance and while the mpg isn't as good, a lot can be said for just opening the door and camping.