Beautiful, but I don't want to see this in the wild. Knobs are bad for the same reason that pie charts are bad. Perceiving one-dimensional differences is easier than rotational/angular ones.
Not really for ratios. If there's a min and a max, sliders make sense.
You can make a better argument for a knob if you have an unbounded range, or an effectively unbounded one (making small adjustments on a large scale). Think old iPods.
