I also use the diagonal piece -- if I am doing a small quilt and have enough lenght in my fabric piece. I use the John Flynn method and I have been very happy with the results. I have done this with small prints and larger prints and really like it. Ihave not done it with larger quilts -- though I may have to do it for my son's quilt since the back I want is 90" wide and the quilt is 110" wide.
http://www.flynnquilt.com/media/uplo...onalpb1103.pdf
http://www.multi-patch.com/html/fabric_calc.php
My problem is I drive myself nuts trying to keep the back seams away from the front, this works better for me.