I really like my new Janome 6600, BUT...my only complaint about it is that I've been completely spoiled by the built in walking foot on my old Pfaff! The Pfaff walking foot can be used with the Pfaff feet that have the cut out in the back...most of them do, without having to change the shank, simply pull it down and it snaps onto whatever foot you're using.
I bought the 6600 because of the walking foot, but there is just NO comparison to the Pfaff one, and it's got a strange shape, making it impossible to use the side of the foot as a guide. It's also a pain to have to remove the shank and replace it with the entire walking foot. To compensate for not using the walking foot, I've been letting up a bit on the presser foot dial, like setting it at 2 instead of 3 for straight stitch sewing. It works! lol
I sure wish Janome would make a set of feet that are normal width, use the existing shank, and that would accommodate the Janome walking foot.
I find that the 6600 has plenty of harp space and have had no problem moving a queen size quilt through it.