Good for your for reporting! I'm late chiming in - but I have had mixed responses from cops. BUT most of them have been positive (and I probably would have reported the cop that did nothing, honestly).

Here are my good experiences: A guy passed my DH and I in a downtown area and a motorcycle cop pulled him. The cop chatted with us and gave him a stern warning. A motorist passed by DH way too closely one night and flipped him off. He got the address where the car went. The cop talked to the lady, explained that people always watch and she had better behave better, and gave her a ticket for parking the wrong way on the street. When I lived in a small beach town, an elderly lady cut me off (had to slam on brakes not to hit her) - she pretty clearly couldn't see where she was going. I asked the police if they could at least ask her to be more careful, and they went and talked to her (and called us back). I think most of them (cops) are trying to do the right thing.