My 05 does about 16 around town, although recently I have taken a good hit in mileage so I'm not sure whats going on. Might be tune up time. My uncle just bought a new one and it gets a bit less, but it only has 1k miles on it.
They seem to be a pretty good motor, as long as your not towing it seems to do fine hauling the truck around. I have put 1 ton or more in mine on a number of occasions and it has more than enough power.
One thing I did notice is the new body style must weigh a bit more, my uncles is a dog compared to mine. Both trucks have the same motor, transmission, and rear end gearing, even the same wheels. Mine pulls a lot stronger at all speeds. I need to get his truck on a scale, mines about 4,300-4,400 empty, I think his is about 300-500 more.
I really prefer the older body style, plus they are lower which is nice if you actually use the truck as a truck. Lifting a 200 pound compactor or generator over a jacked up new 4x4 is a PITA, my truck is nice and low and not to bad. Or when I put ramps on it and drive a lawnmower or ATV in the bed, new trucks are jacked up to high, even 2wd. When I buy a new truck I'm going to put a lowering kit on it.
If I were buying a new body style I'd spring for the V8, the 4.8 is less than a G note more when buying new, and seems like the motor to go with.