You make good points, but I'll say first your example of the obvious speed trap is a different problem of which I agree with you.
There are examples of US interstates with no speed limits within, to some people, reasonable limits:
http://www.motorists.org/press/montana-no-speed-limit-safety...
They even discuss how in some cases fatalities go up with new road laws and speed limits.
I have driven that stretch of road between Austin and Dallas as I live in the Dallas area. I have also lived in Florida with it's stretches of long, boring roads. Plus, I've lived in Vegas with that incredibly boring route into Los Angeles. In every case I would agree with you that the idea of being able to go a bit faster would have been nice.
But the question that will come up is how do you determine the maximum speed that you can safely manage? What if your assessment of your max speed differs with that of the police officer who witnesses what he feels is a dangerous amount of speed? What about other people on the road that you will eventually come across that can't handle the situation that you present if you decide that the person can handle a speed that in truth they cannot? I'm sure you're thinking you'll just slow down when you see someone but you cannot foresee the possibilities plus your reaction time dwindles quite effectively the faster you go. A mile at 60 MPH is one thing, a mile at 120 MPH is another.
My example against this, which is interesting considering the topic of this thread, is when I was in Vegas an off-duty cop was speeding (I forget how much but in excess of 100 MPH) on one of the interstates outside of the main part of town and rear-ended a family in their car. The resulting accident killed a number of them including children. Therefore, I personally don't like the idea of a free-for-all on the interstate where different cars can drive at different speeds based on criteria that will be different for each individual driver and car. I would rather we all agree on a maximum speed that makes sense for the conditions of the road and expected traffic. Now if a road has too slow of a speed limit for the typical conditions of that road, then that is a different discussion.