Admittedly, I have factory power steering, but turning the wheel, while backing up in to a parking spot at a show, when the car is stopped, and parking in general, are so much easier, with the knob. The factory PS is overkill, so you can literally do it with two fingers. Actually, I use it most of the time, while driving.
I wrapped the steering wheel with a thin piece of rubber before I put it on, because it will cut into the wheel, to stay in place.