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.