My first ever ride on Son Of Beast was in May 2001, and after two consecutive rides in the front seat, and one in the back, it rated as the roughest ride I had ever ridden, it even gave me two bruises. Halfway down the first drop the train started to shake, and threw me side to side all the way to the top of the second hill and then again during the first helix. The third hill was okay, and the loop was very good, and is easily the best part of the ride. However, after the loop the ride is pretty boring (and still rough), and the tops of the second helix are very slow.
On my visit in 2002, I decided to avoid sitting above the wheels, and to my surprise the ride was a lot smoother, and actually quite good. The ride in the 2nd seat was very smooth, and the only rough part was at the top of the hill before the helix, and even this only involved a bit of shaking. It was a little bit bumpy further back in the train, but still a considerable improvement from the previous year. I almost concluded that the ride had become smoother, but after riding again in the front seat in 2003, this was a mistake.
In addition to the roughness, the trains are extremely uncomfortable, in fact it is probably the trains that further the bouncing and shaking experienced during the ride. The lapbars are uncomfortable, and you can easily bang your legs on them during the ride.
If you like or don't mind rough woodies, then SOB is for you. If you don't like rough rides then make sure you don't sit above the wheels. Sitting in even numbered rows, such as row 2, provides are far smoother ride, one that allows you to enjoy the intensity of the ride, without being bashed all over the place.