I wish there were different levels of driver's licenses so a person could get rewarded with higher limits once they demonstrate safe driving behavior. Slow speed limits are annoying, so they'd make an excellent penalty for poor driving, right? I realize that without sophisticated ways to measure the danger speed introduces to a driving environment, the best officials can do is set an arbitrary number for skilled an un-skilled drivers alike.
Personally, when it comes to what speed to drive on a highway, for me it boils down to the conditions, the environment, my alertness... not so much what the sign says. On wide-open highways with five miles of visibility up the road and sunny skies and multiple lanes, safety is common. Inside of towns, late at night, or on roads where a surprise is likely such as a deer, however, I do the limit and don't push it. One small Colorado town warned me with a quick flash of the cherries when I didn't drop my speed to his satisfaction, which I'm very grateful for. Other places, such as the CO/KS and KS/OK borders, tend to be patrolled more strictly.
It also helps to have someone on board who can help explain the reason for speeding. I know of one woman on this board who once gave such a brilliant, Oscar-winning performance in Kansas that even I was convinced she was about to die if we didn't get to the emergency room. I still crack up thinking about it. In case you're still lurking here, S., bravo!