Personally, I don't wash prior to using fabric because I LOVE the look of a quilt that has the little puckers in it after washing. Plus, that tiny bit of puckering helps to hide any mistakes you've made. I'm not a perfectionist when it comes to my quilts because I'm of the opinion that any imperfections that still show tend to let the recipient know that I loved them enough to continue on with their quilt in spite of any difficulties I might have faced with it.
Donna