Hi there Dlaporte, I'm a GIMP man myself (though I also use Inkscape and Wilbur as well). I think overall it will allow you much more versatility than CC3 or Hexographer. With GIMP you can create a variety of different styles of maps, whereas with the other programs you are limited to the symbols/icons installed in the program. Now, in the plus category for CC3 and Hexographer, once you get past the initial learning curve of the former, I'm told they are very easy to work with and map creation is fairly quick and easy (though I can't comment on the veracity of this report). With GIMP there will also be a learning curve, and many maps styles (though not all) will remain somewhat time-consuming even after one is familiar with the software. However, you have allot more artistic freedom and power with this software, and that is ultimately why I went with it. Inkscape is another good free program to have around as you can use it to do line work and text placement much easier than in GIMP.
Now, if you want to make a long term investment, Photoshop would probably be the way to go. However, I'd mess around with GIMP first to see what you think of this kind of raster program before making any such investment. My 2c.