It is interesting how opinionated people are. Personally, I think we just don't know enough to do a reasonable assessment. If we had some example of where a knob might be good and then try to understand whether it was good and if not, why not?

One of the issues (in my opinion) is how much control per pixel you get from a control. Certainly a knob has more control factors than a button. If nothing else you can click it and turn it. In the same size, a knob has much more control effect.

The other issue is how easily and comfortable a person can be using the control. This is complicated. If you see something on a screen that looks like something from the real world, then you have an idea of how to use it. And many of us became very comfortable with the old goofy Windows controls. But initial comfort is not necessary. Learned comfort is. If initially we don't know what it can do and how to use it, can we learn and once we do will we be comfortable?

It is not straight forward. The challenge I face is using a very small form factor - a mobile phone screen - to inter operate with complex systems and vast amounts of data.

The fact that it embodies more control factors in a small package makes it interesting.