I recently worked with Bruce Dorn, who was the DP for a feature being shot on 5ds and is a Canon Explorer of Light. He makes and sells this follow focus that is gearless. This doesn't require rod supports and all that, either.
http://www.idcphotography.com/kart/index.php?p=product&id=125&parent=33
that thing is totally awesome. definitely picking up that "run and gun" rig. we use that a lot and i have a shoulder rig that works perfect with it. thanks for this input.