The Dixie's are almost freakishly wide. That isn't necessary for very many situations, and is a drawback in many others. Mine looks narrow to me sometimes compared to some other brands, but when I measure them, they are pretty close. I think it has to do with the design of the rear of the machine as far as looking narrower than another one might.
As far as hills go, I take mine anywhere that it is safe for a Z to go with no problems yet. The run flats do make the ride rougher than pneumatics do, but then you don't have to worry about flats either. I guess it's a bit of a trade off.