I have played the JTV-89 today. Indeed, the knob is a smaller problem than I thought. Nevertheless, it does interfere with my playing a bit. Fortunately, if I cannot get used to the knob position, I can easily remove it, leaving the axis bare, which offers just enough space for my hand. Another thing I do not like is the little "step" on top of the body near the strings, where my fingers often like to float unhindered. But I guess a little piece of plastic attached to the body will solve the problem. Apart from that, I was pleased with the ergonomics. I got the impression that it is a surprisingly light guitar.