I love having a steering knob. When your doing hay it makes turning back in on a row much easier than having to spin the steering wheel by and and gives a general reference on when your wheels are straight again. I also like it for loader work as you can keep one hand on the loader controls and the other on the knob. Palming a wheel for hours on end gets old fast. Anything to make life easier when spending hours on the tractor is worth it.
It is annoying how the know ends up in random spots due to full hydro steering.