I had the opposite impression. I had a 2013 rental and I hated it. I much preferred my 2012.
First thing I hated was the auto transmission. That drove me nuts. My car is MUCH more responsive.
Second complaint was with the silver plastic pieces on the steering wheel. Being only 4 months old it was already scratched and marred and looked like it was closer to 10 years old. I'm glad I don't have it in my car.
Don't like the nose, but the tail lights were nice. Gas mileage was MUCH lower than mine, despite having the same engine.
All in all I'm glad I got a '12. I wouldn't have bought a Mustang at all if that '13 rental had been my only experience with one.