I have an RV Queen size mattress that we bought from Denver Mattress a couple of years ago. We love it - found it so comfortable that we bought a full queen one for the house as well.
They have a pillow type top and although the underlying mattress is of a type of memory foam, it was explained to us that is made of multiple smaller (rounded) pieces that act like memory foam springs.
Can't describe the construction in detail without taking it apart, of course. All I can say is that have suffered from a bad lower back for 40 years, and this is the most comfortable mattress I have ever owned.
Had no idea that they are being pushed at RV shows or by Lippert. We only found out about them when we were shopping to replace our old cruddy mattress in the 5er - we had been using memory foam pads on top of the original mattress and it was awful.
We were in one of the Furniture Row stores and were surprised when they told us they made them in the size we wanted.
They are heavy, mind you, and I had to install plastic sheeting under the mattress so that DW and I can move it when making the bed!