Yes, Sprinter vans are very bouncy as you are sitting behind the rear axle. Saying that, we have made three separate thousand mile trips with our son and grandkids. It was no joy ride but kids can take it. Adults would hate it. It is not all that noisy. It is more annoying when the wheels go over pavement joints. You can still watch DVDs OK on the TV.
All vans are just as bad I think. We did a week long tour in the Dominican Republic last August in a 13 seat Toyota Euro like passenger van they don't sell in America. The back row of seats were to be avoided but someone had to take them.
I exercised my family patriarchal authority to avoid the back.
There is a solution. It is called VB Air Suspension on the rear. Only Advanced RV offers it at this time. I test drove an Advanced RV and also sat in the back in it. We ordered it. VB Air Suspension is a Dutch company and they are Mercedes Benz approved for after market installation.