I use straight-grain binding almost exclusively because it is so much easier to work with than bias. When I do bias-grain binding (usually just because I want a candy-cane stripe on the diagonal, but bias is also necessary for curved edges), I have learned from experience to prewash the fabric (I don't usually prewash); otherwise shrinkage can create a wrinkled binding and skew the quilt from square. Also, if using bias strips, I heavily starch the fabric after prewashing so the bias doesn't stretch on me while sewing. It's so much less work to use straight-grain, that's what I usually use.