rfs, Its a technique thats been around for a while. I use it alot and really like the effects. I've been calling it SYS, for Soft Yet Sharp. I don't remember where I heard about it, or what it was called.
I think one thing that drew me to the technique is that is resembled the look of a Nikon Soft #2 filter that I used to like the looks of, however it did soften everything. But it was the way it softened that I liked, where it bled the light areas into the darks, rather than the darks into the lights like a Tiffen black net or black stocking would. Being able to get the same effect with softening, but also blending and ghosting, then sharpening up the details is real nice.
Typically, I always sharpen facial features as well as select parts of the rest of the image. Usually there are some very soft areas, and some very sharp areas in all my images. The skin tones are always left soft and blended. In the example below, I sharpended up the print in the top/skirt, shoes, straps, choker, and some of the cage behind her. The eyes, lips, eyebrows, and some facial lines were also resharpened (or unsoftened) with the history brush. I will also do some streaks in the hair at about 50% opacity to keep the shimmer and softness in the hair, but add a quality that makes it appear sharp as well.
The image you posted is a very good example of the technique. Nicely done, and a great looking model to boot!