I think it's pretty smooth all around. You can feel it when you come off the brakes, but I don't think it's anything abnormal. The only time I've had some jerkiness from the motor is after I had it locked. A few times it would have a chattering to it. I just stop and turn it off and back on again and it's fine.
Are you unlocking it while riding? I think that's when mine would act up.