Ford unwrapped the new 2015 Mustang today, and it is a very handsome car. Personally, I think they struck a good balance between retro styling and the Ford corporate styling, mixing classic Mustang bits with the new Fusion in reasonable proportions.
I did this quickie photoshop to compare the outline of the old and new. You can see the basic proportions are the same, with a long nose and a fastback roofline, and a stubby rear deck. There are some surprises here. The new car is noticeably more compact, which enhances the low-and-wide aspect of its stance. Notice how the hood line is very horizontal, and then has a pronounced curve downward towards the shoulder line, which includes the top edge of the headlamps. On the rear quarter, there is less pronounced of a curve to the shoulder, but the rear pillars seem to move inwards quickly, leaving pronounced horizontal shoulders, which reminds me a bit of the Camaro. Also notice the very vertical front nose profile. And the old "hockey-stick" curve near aft of the doors is gone.
Part of the reason for the pronounced curve of the nose and the very flat front, I think, is probably the aggressive Euro pedestrian protection regs, which require crush space so that pedestrian legs and heads take less damage from car-people collisions.
Overall, I think the 2015 Mustang is a very good design, which balances the needs of style, tradition, and all the other less obvious requirements such as aerodynamics and crash safety. It is more conservative than I personally would have liked, but fresh enough to not look like a rewarmed 2010 model.