I have a Janome 6500 now for the last 7 plus yrs. I like it because it has no tension problems, needle up or down option, knee lifter (lifts the foot by pushing my right knee), automatic thread cutter (push the button and it cuts it), larger throat opening, for the features more afordable and more quilting smart then many other nice machines. I would not buy a machine that does not have the needle up or down position option or does not have an automatic thread cutter. I would buy it again and feel no need to get the 6600 or the newest Horizon as I am very happy with the 6500. There are several more people that feel the same way including a LA quilter who uses the Janome 6500 along with her Gammil for quilting jobs. Some things that come to my mind are dependable and a pleasure to work on. We own 4 Janomes. I looked at buying a used Janome 6500 for my DD but cost prevented me from it. She works on my 3/4 travel machine Janome Gem, which is a wonderful little work horse too.
I have a friend that has a Viking and she did not like it so she bought a Janome Gem Gold and quilts on that. The machine she bought is a small travel machine but she likes it and does all her quilting on it.