We haven't been on any extended trips yet so it may be premature to comment on how well the Sumo Springs work long term but I have driven the rig around our back roads and have about 150-200 miles on the truck since we loaded the TC and I think they are working pretty well. With just the upper stableloads I felt the truck wouldn't have sufficient anti sway control. The 2800 pound Sumo Springs are just touching the bump stops with the camper loaded so as the camper wants to sway the Sumos are already engaged and take up a lot of that tendency very quickly.
I did not drive the truck with the camper without the Sumos so can't comment on handling before and after but I am a believer in more control is better than less and the truck with the camper is right at its front and rear GAWR so I wanted a little extra.