I have the 6700.......for the same price I wish I had tried the 9400. I was trading in a 7700 that needed a new board and could have either for $2800. I spent so long trying the 6700, and loved it, that the shop was about to close. I would have had to drive back another day, and I was in the middle of a Christmas quilt....so I bought the 6700. When it sews it's a joy....perfect stitches.
I never know when I sit down to sew if it's going to be giving trouble. It's fussy about thread....CANNOT get the tension correct on all cotton C&C....OK, I can live with that. I had a HUGE problem with the corner of a quilt binding. Of course, I had 3 pins in it, but well back from the stitch line.....NO WAY was that machine going to sew that. Even after cleaning out the knot I could not sew at all, even on 2 pieces of quilt scraps, until I completely re-threaded from the spool. This went on several times until I gave up and glued the corner, then it sewed right over that thick corner.
I have trouble with the threader, but maybe that's just me. But, when I try and it "misses", the thread either breaks off or tangles around the needle, so it takes time to be able to try again.
I am not new to sewing or Janome, had 6500, 6600 and 7700, all of which I loved. In all those years of sewing I only once took one of them back to have a nick on the hook polished off. Three times with the 6700 I have said to my husband, "This has got to be taken in.". Usually if I continue to fiddle with it, I can figure out what it wants, and get to sewing. IMHO, I should not be having this much trouble sewing quilts.
OH, another thing is that occasionally the accu-feed disengages....for no reason. I quilted and bound a door quilt (50X72) in the last two weeks, and pieced some batting with a wide ZZ without that happening, yet last night when I went to quilt another quilt, it disengaged 3 times. Then I got about 1/4 of the 57x90 quilt done with a serpentine stitch and every thing was great. My dealer's wife admitted to me that she had had this happen to her, too, infrequently, but could never pinpoint what the was doing at the time to figure out the cause. Same for me. It's not caused by changing the accufeed or the soles. It happened the first week I had the machine (just before Thanksgiving) and then not until last night.
I just wish that I had taken the time to try the 9400.........The dealer does not do trade-ins, so I would have to sell it on my own. When everything is just right it sews beautifully.