Photo retouching is a big part of Photoshop and commonly used in magazines, books, advertisements. It is not too exaggerated when saying that you see this kind of work every day even if you are not a graphic designer. Various methods can be used to achieve stunning effects, sky is the only limitation. However, it is definitely hard to master and requires you to have strong understanding about layers, color and brightness, sometimes filter effects as well.
Elizabeth Wessing did an excellent job on utilizing all retouch tools, such as Dodge, Burn and spot healing to name a few. This was some minor surgery that she performed on the artist Prince. Keep up the good work!
Joe Roenker IMC/Intro to desktop Publishing