I use polyester often, along with cotton, cotton along with silk, silk along with wool... In other words-- I use many different Threads, without problems. No one knows except me. I also use many different fabrics. I've made quilts with batiks and flannels together that are great, velvets, wools, silks with cottons... Sometimes I think people stress over little things that really don't need to be stressed over. As long as your thread is good, strong and the color& weight you want to use, use it. No one is going to say your quilt isn't good because you have polyester thread in the bobbin-- no one is going to know.