I support both the Gimp and PSP. I've used both in my time (before finally getting a copy of photoshop), and they work fine. Especially if you're just starting out with this stuff, they have all the features that you'll need. GIMP is a little bit more complicated for newbies, but overcoming the learning curve for graphics programs in general makes up a lot of it, so you should be fine.
Of course, at this point I've used Photoshop for enough years that going back to the other programs is hard, though I do keep PSP7 on my computer for doing quick things that don't merit photoshop's start-up time.