I understand the basic pros and cons of ultrasonic lens motors — called USM by Canon, SDM by Pentax, or SWM by Nikon. One of the chief benefits is that they allow "always on" manual focusing — you don't have to disengage the autofocus motor in order to make manual tweaks.
Many Pentax lenses using the traditional non-SDM have drives have a quick-shift clutch mechanism which accomplishes largely the same effect, but this is apparently different. Is the difference here something to do with the motor itself (and something to do with its "ultrasonic" nature), or is it that the gearing used by this type of motor is special?
It's my understanding that some ultrasonic motors are ring-type, but that others, including the one in the DA★ 200mm lens I'm testing, are "micro-motors". Both seem to have this same beneficial property of allowing manual focus without a switch, which leads me to wonder: would it be possible to use an ultrasonic in-body motor and get basically the same benefit — or does it not work that way?