I too have the 6600 and love it. However no one mentioned this...even using the 1/4 foot for piecing, I couldn't get an accurate 1/4 in seam. The teacher in a class I was taking said I needed to change the needle position from 3.5 (which is it's default setting) to 4.5. After I did that, I got accurate 1/4 in seams. She also had the 6600 and discovered this. Thought I would pass it along.