I have the 6500 and been sewing on it for nearly 6 yrs straight. I was told the 6600 was more desirable because of the walking foot build in. I have had issues with it sucking down but I have with all machines including none Janome. I bought a straight stitch plate and make sure to always use the right needles for the project. I have done a lot of piecing and quilting on the 6500 of very large quilts. I like the needle down position option, build in thread clipper, knee lifter and larger sewing bed. I also do not have tension problems which I did with Pfaff and some other machines. The stitches are very consistent.