I still drive the speedlimit on GPS measurement (and when available those speed measure points next to roads), but if some asshole is going like 20 over then I slow down to 1 km/h below on the dash.
I just put the speed limiter to the limit +2 km/h, why +2? Because radars won't pick that small difference and drivers usually when trying to go to the limit they go a liitle bit faster and it's annoying to have people pass you all the time.
It IS satisfying sometimes watching some asshole try to weave in and out of lanes to get ahead in your mirror, only to just barely miss being able to cut you off and have to get in behind you.
Surprised this is getting as many upvotes as it is. It totally depends on context. I've seen posted 35 mph speed limits on 6 lane roads where every is going minimum 50mph, even with cops in the flow of traffic. I've also been on 2 lane roads (e.g opposing traffic is directly next to you) and the posted speed limit is 55mph.
If you're doing the speed limit in the second one, well done. If you're going 15-25mph below the flow of traffic in the middle or fast lane, because of a posted speed limit, that's a problem.