Radar detectors are a great, granted you use them how they are intended to work. A radar detector will not help you at all if you are all alone on a road and the cop tags you. It will go off when he hits you, and you're screwed. The key to using a radar detector effectivly is driving in packs. The radar detector will pick up the radar put on other cars to warn you it is coming.
As for people saying they are a false sense of security? lol. I own a Passport 8500 and a Valantine One. The Valantine One KILLS the Passport as for early warning. The One will pick up a speed trap over a mile away if the conditions are right. Hell, the other night I was in the Saturn (with the 8500) and it picked up a cop on the side of the road over a 1/2 mile away. He was hitting the people 1/2 mile in FRONT of me, because he was so far back that there is no possible way he could have seen me 1/2 mile away. Once I got up to him, I was going 5 under and smiled. The Valantine One is the best investment I've ever bought. It has saved me, especially on the interstate, numerous times.
Nick