I have the Janome 1600 QC and it is fabulous - I have a frame for it to quilt with as well as piecing. I also used it last fall to stitch a tarp to cover our boat - the tarp needed to be shaped a little. The machine handled it fine. I've used it to sew leather on cuffs of a barn coat. I recently used it to sew velcro onto bags for a snowmobile. My husband thinks a sewing machine can do anything, and since he helps make things for me and my quilting, I try and fix/make what he asks.
I can't speak personally to the Juki, but I have heard lots of positive comments from others about them.