Missi:
I, too, use old mattress pads for quilts, tablerunners and placemats. I've also used them in potholders along with the heat resistant material. They do work great. I make lots of quilts to give to the foster care program so the old mattress pads work great and help with the cost of making the quilt. I always use new fabric for the outside and if the mattress pad has a stain I don't use the stained part in the quilts. They do work great.
My mom made quilts when I was a kid and always put old blankets between the top and the back fabic. I have a 60 year old quilt that I use everynight to snuggle in that my made that has a wool blanket sandwiched in between. I love it.