I have the 4100QDC which I assume is the older version of the 4120QDC (the only difference I can see on the Janome site is that the 4120 has a built in thread cutter and the placement of the screen is different). I only use this machine for quilting; I use my antique Singer 301A or Featherweight for piecing. I have been able to quilt up to a queen size on this machine. I have been mostly happy with it. My only complaint is that when I'm using my walking foot and sewing very fast, the needle falls out. But that could be a maintenance issue as I have not had it in for service in the last 2 years. So I just adjust the stitch speed to about the middle, and that works fine. (It also helps me to sew much straighter, too, so it's not necessarily a bad thing!)