I am using my Janome 1600P. I bought a new carriage with control that will fit my Janome and a speed control to go with it. However, I continue to have problems with thread breaking at sporadic intervals. Everytime I think I have it licked, it happens again. Someone gave this one to me. She had been trying to sell it with no buyers and she just wanted it out of the way since she had a new "real" longarm. I probably paid another $150 for the carriage and control.
Even with all the problems, I would still rather work with my quilts loaded on the frame than to try and make a good quilt sandwich for quilting the regular way.
Oh yes -- forgot to mention that my HQ is one of the older (maybe oldest) models.