GIMP is a free copy of photoshop. I have nothing to say against GIMP because it is free and come with linux. It is the best alternative to photoshop but of course they cant beat the king of digital editing like that. Makes a while Adobe is in the game and they wont loose their crown yet. You must also admit that you really pay for the difference.
I havn't used GIMP, so cannot compare, but Photoshop Elements is the way to go for a much cheaper version of Photoshop.