Not really, it just has a steeper learning curve than Photoshop, and the UI is a little harder to get used to.
i doubt ill be able to get it gewd, but ill try =)
I'd beg to differ, I used photoshop -first- before GIMP and I think GIMP nailed the UI and most importantly, the shortcuts. I mean in photoshop: M for Marquee tool? I didn't even know what marquee was. Gimp: R for rectangle selection.
Both do the same thing, but Gimp just has a better name and hotkey to match for ease of use and settling into a new program.
But anyway, whichever you end up with ( most likely GIMP, PS is EXPENSIVE and not at all possible to get freely (sucking up to no warez rule... :P).... not. ) Anyway, search for tutorials on realistic shading and lighting tequniques in GIMP and Photoshop too (both tutorials can apply to each other if you know the tools back to front)