Just got back last night from a short road-trip from Baltimore to Blacksburg, VA. Total mileage was approximately 660 miles. 2014 GC Limited performed flawlessly. Weather ranged from sunny to thunderstorms to fog. Road conditions were from flat straight stretches to Blue Ridge mountains and some twistys, to a gravel road.
Most speed limits were 70 mph and we may have exceeded that slightly a few times.
Averaged 24.6 mpg. The 3.6 V-6 never left me feeling under-powered or lacking torque. Only possible exception was when a guy driving an SRT GC pulled along side me in a long straight stretch, looked over and gave me a thumbs-up, mashed the pedal and blew on down the highway.
Got a good chuckle when we reached our destination and had to drive up a pretty steep gravel road and my wife (who actually drives the GC 90% of the time) asked if we could get up the hill. I just smiled and gunned it. We sprayed gravel and blasted up the hill.
Not a very scientific review, but this thing is a great vehicle on highway. Comfortable, quiet and easy to drive.