I am overall very happy with my Liberty, but not happy with the gas mileage. I am averaging about 13-14 mpg on a truck that is rated 16 city.
Other than gas mileage, I am happy with it. It handles great, really comfortable and very nice looking. Interior cabin room is surprisingly larger than it looks from the outside. I have had a 6'4 person sit behind me very comfortably and I am 5'11 in the drivers seat.
Great truck, very comfortable, handles great, sucks gas!
To add a bit of reality to the "real truck" perspective I offer this. I too was unhappy with mileage, sometime 11mpg city driving. I also had some delay when the car hit 40 mph. Turns out that the shift mapping was hosed up and they re-flashed the chip. Big difference. I'm not getting 50 mph like the "perfect world" might give me, but its better. And the shifting is smoother. My advice is to take it in and have them check it out. It's under warranty and Jeep is usually good about such issues.