Does the PF Servo motor, which was introduced in the 9398: 4x4 Crawler model, have return to center feature?
Here is another video from Sariel which shows that it returns to center: http://www.youtube.com/watch?v=T_Gvuzsngg8
With the 58122c01 Remote Control Unit it returns to center if the remote is not actuated.
With the 64227 IR Speed Remote Control Unit it returns to central position when the stop button is pressed.
Yes it does, see http://technicbricks.blogspot.fr/2012/06/pf-servo-in-action.html