For all the reasons listed above, I am constantly amazed that we think cotton is the "only" fiber to use in quilts. Poly doesn't shrink, it doesn't fade (especially the black), it is more durable and dries faster. Personally I like the sheen of poly and have no problem using it. I can understand not mixing the 2 fabrics with the sheen of the poly and the dull appearance to cottons. So then, too, why do we like poly battings with cotton tops?
Now that cotton prices are going up, it will be interesting to see if we come around to thinking poly is just the most wonderful fabric again. My mother made a lot of her quilts with polyesters and they are standing the test of time quite nicely--all hand quilted.