Thinking of buying a 2012 or 2013 GC. I rented a '13 SXT and drove it about 300 miles this weekend... if anyone's interested, here are my observations.
Gas mileage was disappointing after seeing people report up to 29 mpg on some posts. I was hoping to see at least the EPA rated 25. I got 22.5 going west from Kansas City to Abilene, then got 24.1 coming back. Of course, as is normal for Kansas, strong winds. They didn't seem to be headwinds, at least not direct; they were coming from the north or possibly NNW.
I know even sidewinds affect mileage, so maybe one trip like this is not a fair evaluation. It was also hilly (yes, there are hills in Kansas), since the route passes thru the Flint Hills area.
I was also disappointed with the interaction between the cruise control and the transmission. 6th gear is pretty tall, so the darn thing wants to downshift on fairly light grades to hold the speed, but it seems too eager. On steep grades, my 2001 Intrepid unlocks the converter to get a few hundred more rpms, usually avoiding a downshift unless the hill is pretty wicked; that's a better answer. As far as I could tell, the GC never unlocked the converter in 6th gear, just shifted down with a roar and a lurch of power, jumping from 1700 rpm to 3000, then settling down to about 2500 as the converter locks up again. I haven't cared for the way they program cruise controls since they went away from the old vacuum operated systems of the '70's and 80's.
Other than that, I really liked the car and will probably be buying one soon.