I have one and love it. I think for most of us we're skeptical as to why this frame is so much cheaper than the rest. At our last quilt show, John Flynn was there and I asked him about that. He seemed a little surprised at the question but explained that his is the only one where you move the frame. The rest all move the sewing machine itself which requires some mechanical devices hence the extra cost.
I don't think this frame will be feasible for a king-size quilt but I've not done one so we'll see at that point.
It does set up very easily. The only problems I had were from me not thinking before I did things. I'm using a Juki 98Q and don't have any problems.