I have had the 6600P for a month and have been FMQ a lot! Yesterday I bought the new FM foot for it and it is wonderful. I have heard that you can use the Start/Stop button instead of the pedal and set the speed you want instead of having the stitch regulator. Have not tried it yet, though. The bobbin case with the blue dot is optional if you get the new FM foot. My sales lady said you don't need both, just play with your tension settings.
Have fun with your machine...
judee