Modern plastic bumpers and panels have A LOT of reinforcement behind them to help them maintain their shape.
I never thought about the corvette reference, but that is a good point. Personally, I've never seen a vette that was so distorted that it was obviously noticeable to me, but I tend to be a lot less picky then a bunch of people I know. Darker colors would obviously highlight this fact over lighter colors.
So, I'd say it is kind of a personal preference of how much potential variation you may want to deal with. Some companys do make street weight and race weight parts, obviously with more or less fibre reinforcement to avoid the distortion situation. Myself, I'd probably go for it. My brother, who nit picks body lines and panel alignments and such, probably would not be happy with something like that.
