Just my opinion, but I think it's better to practice on actual quilt sandwiches. You can keep costs down by using inexpensive batting from JoAnn's in combination with thrift store sheets. When I was learning to FMQ on my domestic machine, I made up about a dozen 14" square sandwiches from muslin and batting, and drew different designs on each. I'm pretty sure the total cost of these sandwiches was less than the cost of the Quick Trainer.
Plus, I don't like taking up valuable storage area with gadjets like this.