Campaign Cartographer, as others have said, aids the artistically incompetent (like me) to produce half decent maps. Thos who have a modicum of talent can also use Campaign Cartographer to produce maps, but of much higher quality. The difference is that CC3 is a CAD package (using vector graphics) rather than an art package (using bitmaps). The difference then becomes ability to zoom in to the image without losing any sharpness.

For examples of what an artist with talent can do with CC2/CC3, just have a look at Allyn Bowker's website. He tends to use Campaign Cartographer and can get amazing results without resorting to post-work elsewhere. (Although sometimes going in to Photoshop for post-work would probably be easier)
http://www.darkleagues.com/fantasymapping/index.html
http://www.darkleagues.com/fantasyma...ique-style.htm
http://www.darkleagues.com/fantasyma...rlandviews.htm