I too think it is a matter of preference. I do pre-wash my fabrics. I just feel better knowing they are clean. When I iron them afterward I use a product called "Mary Ellen's Best Press". I love it. It is called a clear starch alternative. No ugly white flecks when ironed. It gives the fabric just enough stiffness to allow for easy quilting.
Thanks for the idea of clipping the corners. The fraying at times did bother me. Now I'll prevent it. YEAAAAAA