A radar detector is no replacement for autonomous visual surveillance. If you're driving normally, you should have yourself trained to automatically spot cops. If you're driving fast, you should be actively searching for any reason to slow down-- be it a cop, a dip in the road, an oil slick, a car that could become an obstruction in the near future, etc. I want a radar detector, and I'll probably get one soon, but to me it's no excuse to relax on visual scanning. You've got a lot more things to worry about than a hefty ticket when you're blazing down a road.