I purchased my 2013 base model 6 spd GT in 9/12. I really haven't spent a dime on the car that wasn't a 'self inflicted' modification.
I wanted a wanted a tighter firmer suspension so upgraded with the Ford Racing suspension, 3.73 gears, and wider wheels/tires. It may now be too firm for some, but it handles great. If I were to buy it again, I would have 'pony-ed up' (sorry - couldn't resist) for the track pack with the additional display. MPG? - eh, well - I didn't buy it for that. Best I've seen on hwy only is 22, I average probably 16-17. Oh - my girlfriend is 'petite' and needs a booster seat to see over the dash so if you are short you should be aware of that.
Power on demand. Comfortable for my size (6'5"). Huge aftermarket to modify/personalize the car.
Gas mileage sucks but I didn't buy it for that. Stock GT brakes will fade under track use - get the Brembo brakes if you intend to attend HPDE track days. Stock manual shifter is balky under spirited driving - after market shifters are much better.