I was never a Mustang fan, they never seemed that nice. But now 2010 and up cars have pretty high quality interiors. I'd place the inside in line with 90's-2000s BMWs. I think it is important to realize just how good that is at this price point though. The 2011 got the 5.0 engine. It is a great powerplant; a piece of engineering at this price point. It would not be out of place in a car double the price. I know I brought up price in this twice already, but you just can't help it. Mustang has seriously become an absolute bargain for what you pay. It is a solid built performer that is great to drive. They are a bit heavy, which detracts from the driving some, but it still makes an outstanding GT car.
Fun to drive. Tremendous power. Precise handling; goes around corners on a rail. Ride may be a little stiff for some (see the precise handing comment). Gas mileage around town 17-19 mpg. On the freeway low to mid twenties. Electronic package has some nice features but you don't buy this car for the electronics. If you are thinking about a Mustang I would try to do a comparison test drive of one with the handling package and one without. The stiff ride may be a negative for some. Many positive comments from friends and passers-by (Deep Impact Blue helps).
If you're looking for a fun car which gives you a sense of pride every time you step in, look no further than the Mustang. I purchased the 2011 V6 and, although it's not as powerful (or as loud) as its V8 counterpart, it's a joy to drive. After a long day at work, climbing into the Mustang for the drive home makes it all worth it. I have the six-speed manual and it shifts cleanly and smoothly. The ride is extremely comfortable and the acceleration is excellent for a V6. Although its a larger car, it doesn't feel like it once you get used to how it drives and handles. This is one of the most fun cars I've ever owned. With a large assortment of aftermarket accessories to chose from, you can easily make your Mustang 'yours'.