I have a Whistler that I've owned for 10+ years. I have learned that there are three things that help you avoid speeding tickets.

1.) Watch where you are going. A cop using a laser gun has to have you in his line of vision. You can see him as soon as he sees you. But once he hits you with the laser, you're toast. Also, pay attention to where the cops in your locale tend to hang out. In Indianapolis they patrol any construction zone and any recently completed road work constantly. Just be smart. In most cases you will be able to avoid a ticket simply by keeping your eyes down the road. You should have at least 15 seconds of eye-lead time, meaning that you are looking down the road at a distance that will take you 15 seconds to reach. Farther is better, but sometimes you can only see as far as the next curve. But no matter what, your eyes will save you more often than your detector.
2.) Watch traffic around you. If people ahead of you are tapping their brakes, slow down. There may be a cop or some obstruction on the shoulder. Either way, slow down and see before resuming your speed. I see people all the time who swerve into the left lane in these instances only to fall right into a speed trap.
3.) Listen to your detector. You will learn what makes your particular radar detector respond at certain levels. Mine goes from 1-9. If it hits anything above a 2, I slow down.

I have not had a speeding ticket since purchasing my detector. (I bought it after receiving my one and only speeding ticket.) I don't think it makes any difference what you buy as long as it's not from the dollar store. Just use it sensibly and be safe.