Lots of good info here...addressing "quality" tho....i think you need to look at thread count. The fewer threads per inch, the less wear you will usually get from the fabric. A magnifying glass will help - count the threads per half inch and compare a questionable fabric to a suitable fabric.
RE: using / mixing polyester....i agree that it works just great - so long as the cottons you use have been preshrunk - cuz altho polyester melts, it rarely shrinks. OH....and don't use it for pot holders !!! Don't ask me why i know this please.