It helps to bring your own fabrics. Dealer-supplied fabrics are always chosen to make sure stitching is perfect, so they are usually heavily starched. I would also bring a practice quilt square basted in your usual manner to try out quilting with the built-in walking foot and also FMQ.
For me, the sound of the machine is important. My Bernina just sort of purrs; I don't like a machine that makes clunky sounds!
I would try out a few of the decorative stitches too.