I've got about 1000 miles on my new Mustang GT. It's a terrific car to drive, fit and finish is nice, it's got a great engine and exhaust note, and a very, very addictive gas pedal.
My only pet peeve: The road noise coming from the back wheel wells. I think this is one area where Ford was a little scimpy with the sound insulation (there isn't any). I love to hear the exhaust, but you can hear every little grain of sand come off the tire and hit the underside of the wheel wells, and it's especially noisy when it's raining. I had a 1989 Dodge Omni that didn't have any where near this much noise in the back, and that car was a real cheap POS. I think this is a little rediculous in a car that otherwise has a great, comfortable interior.
Just my 2 cents. If there were something I'd want Ford to change for future Mustangs, it would be to put some sound insulation around the rear wheel wells. I'll be doing my own next spring with dynamat. Maybe some around the transmission tunnel as well. That's a lot more noisy than past generations as well.
Great car otherwise though, as your sales certainly show. The most comfortable Mustang ever. Also the best looking car Ford's made in many years. Keep up the good work.