I'd have to disagree. I think the New Edge, S197, and 1964-1978 all look better. I'm not crazy about the S550 exterior (Shelby GT350 excepted), but the interior of even the base model is sublime.
I test drove a 2015 GT when they first hit dealer lots and the interior/ergonomics of the S550 was definitely a huge improvement over my 2014 GT. The brakes and ride quality were a lot better too. I still prefer the styling on the S197 but the S550 has been growing on me over the years.