Hi- I have had the 6500 for about 7 years and just love the machine. It is a work horse!! I do alot of quilt piecing w/ it and it is fast and sews beautifully. I love the knee lift, the cutter and take it to classes w/ me all the time. A friend of mine just got the 6600 and is also delighted w/ her machine. I considered getting the 6600 but other than the special set up for the walking foot there is virtually no difference between the 2 machines.