As a dressmaker first and quilter way later, I am a stickler for cutting anything on one of the grains. Especially if it's ever going to be machine washed. Yeah, you may be able to finagle the piecing and even quilting without stretching pieces, but once it gets washed it can twist and distort if off-grain. When I shop for clothes or anything else made of fabric, I always look at the grainlines as a scale of quality. Off grain = poor quality control= reject, in my book. It would drive me nuts to look at a quilt cut all helter-skelter, so I am not going to make one! Whatever little bit I might save in $$ just wouldn't be worth it to me. (Stepping off my soapbox now...)