I recently bought a fab u motion without stitch regulator from a board member. I haven't tried it yet because you have to have a machine with the part that you remove the do sleeves. You sit you machine on the mover and it have a very narrow opening and none of machine will fit. I have one more machine to try on it.
Frankly, I don't think the are worth $500. or the price I've seen with the stitch regulator.