My issues with the car are the ugly hood heat extractors and rear spoiler on the GT. A spoiler delete is easy, that appears to be an option. But the hood extractors not so much. Maybe they will fix those by 2017...
Agree with the OP about the body color rear diffuser. I've seen one in dark grey...
The latest renders look amazing. The headlights look just a little wonky though, like they don't quite follow the rest of the body's styling. Maybe that's the way the production car will look but I think it should flow a little better.
For those that don't remember, C&D also released some very accurate renders of the C7 Corvette well ahead of the official release of photos. I like Chaz's renders but I like C&D's renders a little better. But they are both very similar as another poster mentioned.