Long story short: What I thought would be a 30 minute rural test drive turned into 2 hours of track time on the VIR full course.
Not mine. Base 2015 GT, manual trans, and a very handsome Guard Grey(or is it green?) color.
Drove a '14 here last August. The '15 is leaps and bounds ahead of the 2014 Mustang. It is certainly heftier, but so much more poised. I'm accustomed to the raucous feel of the old GT's (solid rear axle=never a dull moment). Honestly, the '15 felt a little too refined (for a Mustang) and a bit bland on the road on the way to VIR, but on the track it really comes to life. Has a nice, predictable understeer that you can swap for a nice predictable oversteer with a little extra brake pressure, the new rear suspension tames kerbs that would make the '14 get a little too unsettled, and the rear stayed nice and planted at 130mph over high-speed rises that frankly gave me the willies in the old car at 120. Very easy to drive fast, very confidence-inspiring. They say that Ford did all that could be done with a solid-axle on the last cars, but this is a huge improvement. Lovely car. I like it.
I actually like driving the all-season tires on the track. I'm fairly novice, and it's nice to feel things start to break loose before you're pulling some really high G's. The last car I drove had a performance package and the tires had waaayyy more grip than I wanted to use. The only time it felt good was when I picked up too much rubber marbles and it got a little looser. When I'm a better driver, I might prefer some semi-slicks.