I have owned a juki 2010 I bought her as a package with the grace quilting frames. She is a workhorse of a machine, beautiful stitches when free motion quilting. I used her specifically in the frames for "long arm" quilting. You have about 9 inches of throat space which was plenty for me as a stipple pattern is what I love to do. I regret selling the machine and my frames every time I go to quilt.( I sold the frame and machine due to space limitations the frames take up a lot of room.) She was not picky with thread, never experienced Tension issue with her either. She sewed fabulously straight out of the box. I also own a juki f600 and I love love love her. She is never complains about thread either, never a tension issue. Jukis are fabulous machines never a regret with either of the machines.
Just a note i also have a janome s5 she is picky with thread but fabulous to free motion quilt with. She is an awesome machine as well but honestly I love my Jukis better.
Thats my two cents for what it's worth LOL
elizabeth