Here in the US, it seems that the posted speed limit is merely a suggestion to most drivers as it seems to be largely ignored. In my town, the speed limit is typically 45mph with plenty of stoplights. My observation is that most drivers drive closer to 55 than 45, then you have those that drive 30mph.
I am one of those that actually drives the speed limit and I even set my cruise control to it. I get passed by the drivers going 55 yet end up next to them at the next stoplight since speeding doesn't really seem to buy them anything.
So do you drive the speed limit or completely ignore it?
My car is a company vehicle which is equipped with a GPS transmitter, both as an insurance requirement as well as a monitoring function. If I exceed the posted speed limit by more than 10mph by manager gets an email, but I have to maintain that >10 for a mile or two so as to give me the ability to pass or if coming down a steep incline. If my speed goes over by more than 20 them my manager, her manager, and the fleet manager all get an email and my ass goes into a sling.
Since I have driven under this for so long I find myself doing the same in our personal vehicle as well. LEOs seldom bother if you are within 10 of the limit and are traveling with traffic.