I shopped almost exclusively on Amazon this Xmas because I couldn't get out of my house due to the weather. I'd imagine many others did as well and this helped Amazon hit their new record sales.
Can you easily stitch panoramas together? Can you take three bracketed photos and use HDR to make one image exposed correctly for shadows and highlights? I'm not trying to flame, I've never used gimp so I'm curious. I'd agree that most of the rest of PS seems like it should be doable in something like Gimp.