I have the 6600 and a Bernina Aurora 730. Hands down the Janome is my favorite to quilt, and also piece on. It is a tough, rugged, workhouse of a sewing machine and it is truly built to last a long time. As far as the tension problems others in the past have mentioned, I have experienced these to some degree. But don't we all on all machines? I know I have before on my Bernina (mostly I forget to check). The Accufeed is wonderful. I mean WON-DER-FUL. I love it, it does not get in my way and in fact, it is great to sew with when doing stitch in the ditch work. My machine came with many accessories, so I've not had to buy anything additional. I will say that if you do buy it, buy the table as well. I love that table and it is perfect for the 6600.
Again, I cannot praise this machine enough. It is comparable to all top brands and I wouldn't get rid of mine for NOTHING.
I wish you luck.
Tina