I took a trip with my new 2010 370Z the other day. Only about 500 miles on the car. Tried to vary the speed a bit since it was in the break-in period but it was on the highway so I couldn't do too much.
Anyway, I averaged 69.2MPH and if the indicator is right, got 29.1 MPG.
Now, for a car that isn't even broken in, traveling right at 70MPH, with the AC going, that's pretty darn good!
I bet with a little break in here, a change to synthetic there, and maybe an upgraded intake (Stillen I suppose) this thing could make 30MPG on the highway.
Not too shabby.