with the studdering, is it only at very low throttle input?
some brushless systems have what we call "cogging"
the ESC has to read the rotor position in the motor, and at very low RPMs with a high load(ie, a MT) that will cause it to studder.
as long as it doesnt do it above 1-2mph you have nothing to worry about.
if it does its really bad. LMK. there are some things we can check

this vid shows cogging:
[youtube]http://www.youtube.com/watch?v=GKzS-RB7nVA&feature=related[/youtube]