I've never had problems with layer cakes, but I've always prewashed them. Recently I've been sewing with jelly rolls that are not prewashed, and they are quite squirmy. I'm finding the sizing that isn't washed out makes them a lot slippery than I'm use to with prewashed fabric, and they also don't press well (not a firm crease) and that also caused problems. So far I've used about 6 jellyrolls for three different quilts. Unfortunaly I have about 10 more rolls to use up. It was bad enough that I pulled out 8 packs of charm squares and washed them all.
I am very use to sewing stretchy fabric (use to make custom lingerie) and bias and off grain give me no trouble at all. Sewing with unwashed quilting fabric has not been near the joy and ease that I normally experince.