Photoshop is a really great photo editing program I really have hours of fun with it. Working in layers it allows you to create the coolest shit. There's also animation options which very Lekka (Fun) I don't really know Gimp at all but it looks great what you did.
Well you can do these things with Gimp, too. But Photoshop is a bit more advanced... (more plugins, better brush engine, better plugins...) On the other hand: Gimp is free and Photoshop is quite expensive ^^ And of course Gimp is getting better
I don't know whether I should buy CS4 I will if get enough faves and people like my work ^^
Which version are you using? CS1 CS2 ... I think Gimp might even be as good as CS2 ^^