Often I find effects like that just don't seem "quite right" - I suspect it's due to the package essentially treating the subject and background as 2 seperate zones, whereas in reality, their is also a transition zone between them that you get when shooting wide-open. Perhaps a bit like compositing one subject onto a different background; if you just "cut and paste" it looks (pardon the obvious) "cut and pasted" whereas in a real photo, again, there is a (small) transitional area that (in the case of a composite) needs to be handled with a small inner shadow or blur.