They can help in a lot of ways. I was in a rental car in Ohio and had my radar detector. It was night and I was probably about 15 over at the time. The Statie used instant-on and had me nailed, but I slammed on the brakes anyway, figure I'm nailed but I need to slow down anyway. I ripped the radar detector off of the windshield and put it under the passenger seat.
Got pulled over and he took my license, etc. While he ran my license, a monster downpour started. He came back and stated that since I slowed down so much that I must have figured out I was speeding and that I corrected myself. I also figure he didn't want to stand in the rain any longer than he needed to, so I got off with a warning.
In the past fifteen years I've been pulled over about five times for speeding. Each time I gave them an honest answer - yes, I know I was speeding, and yes, I gave him the accurate number - and each time I got a warning. Only that one time did I have a radar detector. I'm pretty sure that treating them with respect got me further than anything else.
Before that I used to lie and say I didn't know I was speeding, or I didn't know the speed limit, etc. I got a ticket each time.