Looks like it didn't really make it as the "best driving" Mustang......
"Though it managed a higher average g on the figure eight than the Boss 302 -- which we'd still feel confident calling the best Mustang ever -- the 2015 Mustang didn't feel as nimble or competent as the Boss;
It's a bit unfair to be comparing a loaded to the gills regular GT with a specialty, track-oriented variant.
The mass produced versions of the car (Eco, GT) will be the best driving Mustangs ever made when compared to their counterparts from the previous generation.
And I expect the Boss will be thoroughly outclassed by the upcoming GT350, which will probably have a similar mission (track performance) and a price in that same ballpark (probably a little more expensive).
And yes I realize Ford stated that the Boss was their target when testing the GT with performance pack.
It did match the figure 8 time of the Boss and pull a higher g. I don't think anyone said the car would be faster in acceleration than the Boss, just that it would be quicker around a track. And that remains to be seen since we don't have any real track times yet.
Also, Motor Trend is just one review. And they were easily one of the most negative reviews out there.
I'd read Road and Track's write-up. They have the car in the Performance Car of the Year testing and provided impressions from several of their writers and editors.