On my Civic I have these rear vented windows. They are great around town when I'm traveling at slower speeds since they vent the rear hatch and help diminish the "parachute effect."
But what do you guys think happens at highways speeds with the front windows closed. I'll only travel highway speeds with the windows closed and cycle the AC on and off. But with cooler weather now in the Northeast I'm wondering if there's significant aero drag with the windows vented open.