I've been using PDN since v3x and Gimp since v2.8x. PDN is a very good free image editor and is more than enough for most ordinary image editing users. For the "Advanced User", Gimp is a better choice with Masks, Groups and paths, not to mention more advanced plugins. Still, PDN certainly can produce excellent results when properly used.
I often suggest PDN to Windows users, because it works so well.