I reminds me of some of the old luminance layer sharpening techniques I used to use.
Bottom line is, for a lot of newbie users Detail 3 is going to take the art of digital printmaking to heretofore undreamed of levels of ugliness.
But OTOH when used with the greatest delicacy, Detail is good for things like pulling out modulation in textures such as fields of grass, bringing out tonal variations in shadow areas, and possibly brightening up highlights and texture in rather flat bright areas. In most cases you would want to use either Detail's masking, or work with separate layers, masking in certain areas from a Detail processed layer.
Everything Detail does can be achieved by cleaner means earlier in the post processing workflow, if you only one had thought to do it then. It's best use might be to snap up already existing, flattened printing files where it would be just too painful to go back and work with the layered originals. But I have had it in my kit for many years, and have used it once in a while.
Must say it's a worthwhile buy for the money, but it would be mistake to make it a routine part of one's post processing efforts.