Purchased a 2009 Reg. Cab Sport 5spd manual 2.3 with 3.73. The 1st 500 miles avg 23-26 mpg. Currently with 1000 miles getting 28-30 mpg. EPA estimate sticker shows 21-26 mpg.
I think they use a new method for setting the EPA mileage which makes it show lower. When I bought my truck I believe it was 24/29, then a year or two later with no changes it was 21/26.
I have a regular cab, short box, stick, 3.73 gears. In the summer I consistantly get 30+ mpg on the highway (once got damn near 40 on a 100 mile stretch, burned a touch more than 2.5 gallons on my drive to college from my parents house). It's really hilly around here and my truck has no problems with 3.73's.
Went down to Kentucky last spring, loaded my truck down pretty good (two dirt bikes, a weeks worth of gear for two people, me and my buddy), around 900 pounds in the bed plus us in the cab. Averaged 25 mpg on the freeway going around 70 and had plenty of power, even when I got into the mountains.