I purchased this Mustang in Dec 2014. It was an early build, Oct 14, of the new 2015 Mustang EcoBoost I-4 with the six speed paddle shift transmission, and independent rear suspension. The engine is listed as 310 hp with 320 lb ft of torque.
All of my previous Mustangs have been V-8's with a manual, but with traffic the way it is today, I opted for the I-4, and have not been disappointed. Although an early build, the car is flawless, with no squeeks or rattles. The paint is orange peel free. The body work, panel gaps, are also very good to excellent. The interior is another world above all previous Mustangs, in materials used and panel fitment.It is very stable at highway speeds and in heavy cross winds which are the norm out here, with 18" wheels and Goodyear F1 tires.
My mpg has been averaging 28.9, with 95% interstate driving at 80 mph (legal in South Dakota). On a trip to Minneapolis in March, I saw 29-32 mpg, for the 1600 mile round trip. It cuises quietly, with little wind noise or tire noise. And, the optional Shaker Pro sound system is wonderful, when playing my music, from the memory stick I keep in the USB. The NAV system works as it should as does the automatic climate control with heated and cooled seats, which are very comfortable. My iPhone pairs with the car every time and I have had no lost calls. The Voice Activated SYNC system will control everything you want to do and I use it for climate control, entertainment, NAV and the phone, with no problems. I do miss the heated steering wheel from my 2013 SHO when it is -10!
All in all I am very satisfied with this car. I have had one oil change, and replaced the factory fill oil with a full synthetic instead of the blend, and I do use Premium gas. I purchased the Ford Extended Warranty for 7 years/70,000 miles, so this one will be a keeper.