I do use raw edge/fused machine applique, but only for wall hangings. If appliqueing on a quilt that will be washed on a regular basis, I use turned applique because I do not like the fraying danger. A friend teaches invisible machine applique and uses mono-poly thread and a very narrow zig zag with half of the stitch on the background and half on the applique. I have also heard that a tightly woven batique is best to use for this method as it is more difficult to fray.