Having observed in reviewing many driving records that virtually all speeding tickets are issued for more than 10 over, I cruise at 5 over. Regardless, if I am in the left lane and see someone catching up, I get into the right lane.
My state (CO) even has a new law designed to reduce road-rage incidents which requires that, for roads with limits of at least 65, you travel in the left lane only long enough to pass.
I congratulate SGeringer's girlfriend on exercising restraint. I can easily imagine many others reflexively blasting someone who actually stuck his head into the car.