I think it varies. The latest show with Sue Nichols highlighted the new 830 .......yummm.
For the most part, I have noticed the model used before was the former top of the line, the 730. However, some of the same features, like "pattern begin", which helps you restart a pattern at the beginning of the stitch, are available on a variety of models. Ricky showed that feature a few shows back when he was showing us how he did the double blanket stitch (sometimes called a "pin stitch") for his applique.
The "Single Pattern" feature that Ricky showed in the most recent show is also available on a variety of models. I loved that idea!
I also loved the background stitching that Sue Nichols used on some of her applique blocks.