As a complete newbie, I found this thread very interesting. I want to add that I ran across Sherri Lynn Wood's wonderful blog. She says that for her functional quilts, she always uses two layers of batting, a thin 100% cotton layer on the bottom for weight and a low loft poly on the top layer for lift. Check out this gorgeous commissioned quilt she made:
http://daintytime.net/2011/12/20/put...november-2011/