We have the MOR/Ryde suspension system on our 2012 - 3402RL, and have never broken so much as a glass and have been over some horrendous roads, the concrete sections of some highways seem to be the same distance between joints and create a kind of harmonic bouncing, although that is uncomfortable it really does not appear to put a lot of up and down movement on the front and back of the trailer.
The sections of highways that have sharp dips and rises are the killer. As the truck enters the dip the springs compress and the front of the trailer goes down, and the rear goes upward, when you come out of the dip the truck springs unload and there is an upward movement of the front of the trailer, if the dip is significant enough you will have "no" pin weight and in fact the pin box will try to lift off the hitch. This then creates a downward movement on the rear of the trailer, it is the combination of these two actions that cause significant strain on the pin and it's mounting points and flexing of that part of the frame. All of this is exaggerated with a SWB truck as well.
There is one section of road north of El Centro, California that is just plain ugly and will put more stress on the entire RV than hundreds of miles on roads without dips even if they do have pot holes. I have proof of this recorded on my HERO3 camera mounted on the pin box of the Monty.
While there is an improvement in ride with IS suspension it does not eliminate the effects of going into and out of these dips. I do not think the improvement under most conditions warrants the cost, but that is just my opinion.
IS suspension is used almost exclusively in high end horse trailers providing a smoother ride for the horses, however I have seen the same effect on roads with dips as you experience in a sprung suspension like MOR/Ryde uses.
The only way to minimize the effect of these kinds of roads is to slow down, I have learned that lesson.