I purchased the F600 last June. It was working great for a couple of months then I started having problems with it. First, a needle broke and unfortunately punctured the bobbin case. I had to purchase a new one because the machine wouldn't sew proper stitches ($50). After it was replaced it worked great until a clicking sound began and it started skipping stitches. I was in the middle of making quilts for the grandkids when this happened and had to use a 20 year old Janome with a small throat to complete them because I had to operate it at a very slow speed because it sounded like it was going to jam. Fortunately, the vendor worked with me and had me send it back to them and they took care of the shipping back and forth. It is scheduled to be returned today. They made a couple of adjustments and supposedly it's working fine now. I'm not sure I made a good decision in purchasing this machine!
I have been sewing for over 35 years and have never had any problems with any of my machines. I clean my machines after every project and several times during a project if there's a lot of lint. When this machines works, it works great. The stitches are beautiful and there are many but it's really frustrating when things like this happens and since there isn't a local Juki dealer, it needs to go back to the vendor for repairs and it is quite costly for shipping. Good luck in your search for a machine! By the way, I had purchased the Juki 2010 a couple of years ago and love that machine but wanted one with decorator stitches and because the 2010 is such a great machine, I went ahead and bought the F600.