I'd also personally prefer the rotary knob on the left side. You at empeg will run into a problem with the knob on the right side, which probably will sound ridiculous to you and most of the other readers. But I did software design for about 10 years for Rohde & Schwarz (signal generators, measurement equipment etc), and most of their devices have a rotary knob on the right side, and believe me, we had endless discussions... the problem occurs when you use the knob to scroll through a vertical menu or list. If the knob is on the left side, the way it'll have to work is obvious: turning it clockwise will move the cursor/marker down, turning it anti-clockwise will move it up. Now, if the knob is on the right side, exactly half of the people using it will swear the only correct and intuitive way is to have a clockwise rotation move the cursor up (because the left edge of the knob which is closest to the display moves up), while the other half are absolutely convinced that it has to be the other way round. We couldn't solve it, we ended up making it configurable after customr complaints... the only way to get around that is really to put the knob on the left side of the display.

As I said, this is going to sound ridiculous...