Oh goody, a thread I can comment in.
I own this...
First of all l want to make it very clear that GB is one of the most gorgeous colours I've ever lain eyes on which is one of the reasons I couldn't resist. When I was originally buying the car, I was stuck between Race Red, Oxford White (I wanted red interior), GB, and Sterling Grey. Sterling Grey was on hold for early 2012 so I couldn't order it if I wanted, I already owned a fire-engine red car and didn't want another to complement, and to this day I think I regret not going for the white on red the most, but anyway.
Secondly, I want to say to forget about the stripe like many others have mentioned. It is tacky and is more of a throwback than an actual complement to the design of the car. The only exception to this rule is perhaps white on blue stripe which is nice and classic Mustang, of course.
Thirdly, if you are dailying the car, be advised that the GB attracts a lot of attention, some of it unwanted. Much more so than your reds and whites. This applies to the orange and yellow as well.
Fourthly, GB looks great even when dirty AF. This is a plus. It also hides a lot of detailing ****-ups like swirls quite well.
Fifthly, the dark colours offered are quite nice, but the shape of this car needs a bright colour. Whether it is Race, Yellow, or GB. And please don't get black, it is so very lame on this car.
All this said, the colour palate on the S550 is even bigger than it was on the S197.2. Personally, if I were to buy a new car today, it would be between Race Red and white only because after almost 6 years, I am a bit tired of the attention the car attracts (and everyone knowing where I am at any given time if you are in a smaller town). I am also still sour about having a black interior (forced when buying GB), but that's me.
Just my $0.02
I also don't see the point of the Ecoboost over the V6 besides available options.