Bill G
ArboristSite King
The Deere sidehills were quite popular here in the late 1970's and through the early 1990's. I rode in one many years ago and it was quite freaky. My personal opinion is they fell out of fashion for several reasons. The first being in the 80's we were facing the some of the worst times agriculture had seen. The government had many programs to try to offset the losses. Of course cutting production through the use of "set-aside" acres was one. The next was the CRP program. I know I might be in the minority on this but it was actually a program I supported. It took a poop ton of the land out of production that folks should never have been farming anyway. You should see some of the land that was cleared here in the 70's and the hills they tried farming. That ground was taken out through the CRP program. When it was taken out of production the need for a sidehill combine was greatly reduced. The next thing that killed the sidehill was the fact that technology caught up. The companies developed better grain distribution in the threshing system and reduced the 'piling" or bunching of grain in the machine. Some might remember the Gleaners with the blower assemblies. Lastly in my opinion the downfall of the sidehill was simple economics. They just plain cost more and the benefit received did not outweigh the cost.
I even use it with a muffler on a tractor
usually happens like the suddenness of a broken shoelace! 
