SmoothKit allows you to blur without blurring over edges, sharpen with much less ringing, intelligently reduce small image defects, reduce jaggies, blur with per-pixel direction control, and z-blur using greyscale depth images. Many plugins have per-pixel controls, allowing you to vary the amount of blur or the direction of the blur, and many other controls, at each pixel.
As an example, with SmoothKit you can smooth out the skin in someone's face but not eliminate the details of the hair that hangs in front of the face. In addition to 'effects', the SmoothKit toolset can be used to reduce image defects in a much more intelligent manner.
Features of SmoothKit