I have an 06 GT and had not a single problem. It runs strong and has responded great to it's simple mods.
These Mustangs seem to be pretty reliable. Other than a few small problems, there's really nothing that has shown up yet that you need to look out for.
About the only "problem" I've had with my '06 is that on a rare occasion while trying to fill the gas tank, it will click off before being full and won't allow anymore gas to be put in. I just drive it another day and fill it up. On average it's only happened a time or two per month the past 2.5 years. Some have had the parking brake "freeze", windows stop going up/down, factory cd player skip/not play cds... I'd recommend at least getting a tuner for the car if nothing else! It will work fine while the rest of the car stays OEM, but will increase fuel mileage, gain about 15+ RWHP and make the throttle response so much nicer Easily worth the just under $400
Yeah. Speeding tickets. WAY too common. My girl drove my 06 5spd GT from Ga to Cali without a problem. Gas mileage (at lets say average 2.40$ a gallon, and avg hwy of 80-90mph, 2300miles, she spent around 200-250$ or so to drive, loaded down). Car was reliable, had the little defect of the fuel fill, picked up a speeding ticket, and the CD player locked up/shut off after playing several hours of CDs. Other than that, I can't say I've had one complaint. Though...I'm about to do my sparkplugs at 27Kmiles as preventive maintenance... (see read-up on this forum about it)
The only thing you need to look out for is the empty hole in your pocket because the upgrades are becoing endless to make it "yours". I'll bet that I've dropped around 6-7K extra into mine and it has been worth every penny!! LOL Enjoy and have fun! BTW, I bought my '06 for my wife too