Well, depends on the cop, and where you're speeding.

I tend to do around 75-80 on I-95, and I've never had a problem. Gone right past speed-traps too.

Now in smaller towns, where the speed limit is 30...speeding is harder to get away with.
Had a friend pulled over doing 34 in a 30 before, and ticketed...

I do 5 over for the most part, except in little towns. Never had a speeding ticket.

And around holidays, speeding is much harder to get away with...