I'm somewhere between neutral/indifferent/OK to it and sort of like it. I really need to see more pictures, with different colors and from more angles. The fuzzy initial pictures (the yellow ones) aren't good enough to waste any time with beyond "yeah, the 2018 Mustang is coming". The only picture from the rear that I've seen . . . it needs wider wheels and tires. From the side, I think the nose sits a little too high relative to the rear - not much, and it might only take half an inch of front lowering to fix.
Externally, all I'm likely to notice would be the hood line when I'm driving and my opinion on most everything else would be about how well it contributes to function (cooling, head light illumination, maybe reduction of lift on the track, etc.) and whether or not it makes washing the car a fussier process. Otherwise, out of sight, out of mind.
Internally . . . I might be OK with the instrument panel, but I'd have to actually experience it first. There are times and sunlight conditions where the gauges in my '08 GT are virtually unreadable at a quick glance (say, at a track day when you're going to have adverse lighting at least once on every lap). But I know I don't want a huge screen for the radio and whatever else anywhere on the dash. Don't even want a little one, but probably don't have that choice any more.
Norm