The safest speed to go is the flow of traffic. Sometimes that's 15-20 miles per hour over the speed limit. It's rare that cops ticket safe drivers for speeding, but it happens (IME, about once every 5 years). Tickets themselves weren't a big deal if you're a good driver who gets unlucky occasionally, until insurance got involved and started hiking up the prices. Depending on your state and insurance policy, a $100 speeding ticket can end up costing $1,000 or more.

"Police oppression" might be a bit farther than I'd go, because I rarely get speeding tickets. But the speed limits are under-posted and you can get a nasty insurance hit even while driving safely.