I drive mostly at 70-75 on my 80 mile freeway commute and my lifetime average over 11k miles is 44 mpg. I don't hypermile much unless I am experimenting with something, though I do use some conservation techniques.

I take it easy up hills and coast down long hills in neutral, or in gear if i need a charge, and I back off on the accellerator slightly after I reach speed to get that super efficient mode, while dropping speed slowly to 65 or 70 or so, then accellerate back to 75. Adds about 10% to my commute time versus setting the cruise control at 73 (which I do about a third of the time), but I get a little better mpg without cruise.

I have a 2004 HCH so you'll have to take this for what it's worth. Common impression is that the 06 should do better.