for one, GSS is clear plastic compared to the nikon one that's a bit... white? (opaque? translucent? i'm not sure how to describe it, just that it's not that clear)
also, GSS comes with 2 screen protectors, one for the main 3" lcd at the back, another for the top lcd screen.
lastly, GSS is sleeker, thinner, and.. sexier(??) :bsmilie: thing about GSS is, you wouldn't even notice that it's there. how many of you looked at the back of your d90 and DIDN'T notice that white square thing smack in the middle? :sticktong