I've noticed that, too. I do like FMQ with it (although I'm going to be shopping for a sit-down mid-arm this year). Do you mind sharing what you went with for piecing? I was thinking of the 8900, but have read of some issues with the Acufeed feet/ankle breaking on that model.
Pfaff. I did an even trade (no money exchanged hands) and got rid of both the Janome Horizon and the QDC 3160, for a Pfaff Quilt Ambition 4.0 that was used for 1 project. It wasn't even a year old and mine were 4 years old and heavily used. It was also late in the model year, right before the new 4.2 came out and has run perfectly. However, I piece a lot on a Pfaff Passport and that thing never balks at nested seams. It has awesome piecing power.
I have the Sweet Sixteen sitdown now for quilting and never used the Janome's once I got the Passport, so they just collected dust. I was sold on the Accufeed of the Janome, but really missed the IDT. I'm happy now that I have my IDT back. If your going to go to a sit down quilting machine, I would recommend something that doesn't have a large feed dog width and gives you an accurate scant the minute you sit down. I don't have to fuss with width settings on my Pfaff's...just sit down and know it's going to be scant 1/4" with one of their quarter inch foot. They have a newer foot out now that you move it to the left one click if you want a true 1/4" seam and it works great.