To add my 2 cetns,
have a 11 GC Limited 4x4 5.7 since June 2011 and reported all exact symptoms as yours. The Tech from the dealership felt the shudder and agreed with me the behavior was abnormal. Hooked up a laptop and confirmed that under light load the converter engages/disengages generating the effect here described.
Solution: Star case raised with Chrysler, obviously I am the only one with this problem on earth as they have never heard of any other Jeep in this condition.
Never heard back since and at every service I hear the same story.
Now have 20k miles, I can only console everybody with the reassurance that it did not get any worse with time.