I have the 750 and the only thing I had go "wrong" was the threader wasn't hitting the needle eye. My dealer changed it out for me, it only took 15 min. and it's worked like a dream ever since. Now my sister-in-law bought the 710 and that's a different story. She and I purchased the quiltmotion for Bernina together. I've had no problem using it with my 750. But after the first time she used her 710 with the quiltmotion, when she went back to piecing, the sensor on the machine wouldn't recognize what foot she was using and wouldn't sew. It would sew with a foot without a sensor though. She took it back to the dealer and he gave her the one off the floor to use until they could replace her original. Well that one did the same thing. She just took it back today and he gave her a third machine to use. I don't think we'll be using her 710 on the quiltmotion anymore. I can't tell you about the 780 other than they are also backordered. Bernina is a great company to work with so far and my dealer is outstanding, plus they are only 10 miles from my house.