I have one, and I love it!!! Takes all of the strain out of FMQ...I used to get back and neck pain...I don't with this...it DOES take getting used to, though! The foot pedal is just an on/off switch...the speed of the stitching is controlled by how fast you move your hands(the fab-u motion bed, really)...but with a little practice you can get it down pretty fast...because you are not sitting with your foot on the pedal for speed, it changes your posture just enough so that it is much easier on you back, neck and shoulders, (at least for me).
I like it much, much better than FMQ-ing without it...as another poster suggested...go to a dealer and try one out...good luck!!!