On commercial jets, is asymmetric thrust used as part of normal operations?
This paper from Boeing sheds a light on the subject: 


  [A]n intentional engine throttle up or down could create a desired yawing moment followed by a desired rolling moment. Using asymmetric thrust to control roll is not precise because of the lag time associated with engine spool-up or spool-down and should be avoided unless no other means of roll control are available. 


While the paper is admittedly about righting the plane from an in flight upset, and is therefore based on a disaster scenario, the message still applies to everyday flight: asymetrical thrust is not the preferred method of control, as the delay between adjusting the throttle and the actual thrust change makes it less precise for maneuvering than the main control surfaces.