I use one in my truck and, to be totally honest, I think it's one of the best investments I've ever made. Now, I'm no fan of speeding, but on some roads there's just no way that it's supposed to be 45, and don't get me started on highways.
So, for whenever I'm in a rush, a bit of insurance never hurts. And, it's really fun listening to it go off and try to guess how many more seconds will pass before I see Mr.Blue&White sitting on the side of the road.
Make sure to check your state laws. They were illegal in CT until about 6 years ago, and the "scramblers" are still illegal. But the detectors are all you'll need.