I have an auto 2.7 and I usually average about 21-22 mpg. That is mostly highway driving with some driving around town. When i drove mostly around town i would get about 19-20 mpg depending on how i felt like driving that week or so haha.
As far as power, I am fine with power. A little more power wouldn't hurt and a manual would be nice but im fine with the auto. I probably had the truck near the limit with granite in the bed and drove it on some hilly roads for a few miles and it was fine