Looking to buy, what to look for?

My personal recommendation, having driven all of the various options, and worked on most of them (and having owned two of them) from 2005-2014 is to buy a clean low-miles 2005-2010 5spd car, or a 2013-2014 automatic car.

The 5R55 automatic in the 2005-2010 cars and the 6R80 in the 2011-2012 car just lacks the "fun factor" that changes to the 2013-2014 6R80 bring to these cars (including a manual mode). For manual transmission cars, the TR3650 5-spd in the 2005-2010 cars is far more enjoyable than the Chinese time bomb that replaced it (the MT82 6spd).

The 4.6 3v and the 5.0 Coyote both have their pros and cons, but they're surprisingly similar in terms of fuel economy, reliability, etc. It's just a matter of whether or not you want the 4.6 sound or the Coyote sound, and whether the 4.6 being roughly 100hp down from the Coyote matters to you or not.

My personal choice in the summer of 2010 was to buy a 2010 GT over a 2011 because the 4.6 sounded so much better, the TR3650 shifted so much better, and I figured I'd get that 100hp back with a blower at a later date. If I was to buy today, it'd probably be a 2013-2014 automatic car, because the cars were improved that much in that short a time period.