Being a longarm quilter, I can always tell if the customer set the seam and then pressed or not. When the seam is set before pressing to one side, the "ditch" is always straighter and the fabrics lay much flatter. If you want a quilt top to look really nice after it has been quilted, always "set" the seams first. Otherwise, you may receive your quilt back with some minute pleats in the top.