I have the the SEL 2.5L 4cyl and have experienced the same sort of less than stellar gas mileage. It has almost 6800 miles on it now, about 65% of those are highway and the highest it has hit is 29mpg but the city average is only 24 mpg, a far cry from the 33 highway it claims. In addition, I think the transmission feels rough on both acceleration and deceleration and I have had it in for some braking issues that have been present since I have owned it straight off the lot. At first they told me I had warped rotors (on a brand new car) and they spun them. I made them replace them after that but it is still doing a shudder/hesitation motion when I brake. So far I have been very underwhelmed.
SYNC although it also can be frustrating. The Services feature of the phone does not do a great job with some addresses that require lots of numbers and the directions that I can send to my phone only download thru the connection about 75% of the time so as far as that feature it's not 100% reliable.
Better / smoother breaking, smoother transmssion gear transitions thru upshifting and downshifting and less engine noise in the 4 cyl. Plus so far my gas mileage stinks.