I get around 19-20 mpg according to the computer with manual/3.73's.
I drive it daily with a 60 mile round trip commute that is 70% freeway/30% side streets. Stop and go traffic is common on the way home, but I leave early enough in the morning for it to be clear all the way in and usually tuck in to the left lane and keep up with traffic there, which more often than not will be ~75 mph.
Still have not had a chance to road trip it yet, but based on what the computer tells me at a steady cruise, a fast all highway trip would probably get me ~23 mpg. Around here, if you go <70 on the open highway, you'll get blown in to the weeds by texting soccer moms in their Yukon Denalis doing 85.