Situation dependent, for me.
On a handful of roads, it's clear that the "Basic Speed Law" reigns supreme, due to any number of offshoot driveways and side roads, pedestrians, cyclists, mixed-residential and whatnot. Often, usually on the handful of roads in my area that come to my mind, it's lunacy to go any faster than what's posted. Too dang dangerous.
On the highway, though, at least where I am, one would have to be a fool to go anywhere near the posted speed limit in the 55mph zones, as nearly everybody's doing 65+ anyway. Going 55mph is going to force those speed demons to be whipping around folks in order to "get ahead." I often go several miles over the posted limit, in such spots, but not to a point where I'm pushing people along.
On the highway at higher posted speeds, I'll generally go the posted limit, at most a couple miles over, and I'll just be happier to get where I'm going with less drama. The speed demons have plenty of space to route around me and other slow-pokes, and everyone gets what they want.
In slower, residential and similar spots, I'll never go zooming around. Too many threats, risks. Too many unseen potential problems. Plus, it'll end up almost impossible to explain away, if something were to happen. So, better for them and me: going the speed limit in such zones is a no-brainer.
Works for me.