I don't like the feel of poly/cotton. The scrim in cotton sheets is bad enough (and at least I don't have to iron them). I do use poly/cotton when I want to use a licensed fabric - its often difficult to find an all cotton in the latest Saturday morning hero. But, then, I use cotton or flannel on the back.
Secondly, quilting stitches do not generally show up as well on a poly cotton. That same resistance to wrinkles also results in less stitch definition. Probably not a big deal unless you use a really flat batting.
I am not terribly biased against blends or even using other fabrics. However, if I'm going to put a lot of time into this project, I want to use very good quality fabric. Nearly all my fabric is from a quilt shop.