GIMP is great; simple, with all the tools one may need, and possible add-ons.
Don`t hasitate to try it out.
If you do, check a few video tutorials for beginners, especially one with layers, so it`s even simplier from the start. ;)
As a person with minimal graphic skills I prefer GIMP from Photoshop. In photoshop to do the same thing, it took me like 5 times longer. (or maybe it was that Photoshop requires computer with a better graphics to run :P)