I usually run pretty fast (although on the highway, not so much in 25mph zones) and I have never bothered with a radar detector. The problem with them, especially for your situation, is that a cop sitting in a speed trap doesn't have his radar sitting on, he only triggers it when he points it at someone he suspects is speeding, and at that point, all the radar detector will do is let you know about a minute in advance that you are getting pulled over. As Trunk Monkey said, being aware of your surroundings, and watching the road and other drivers can be just as good or better than any radar detector.
An example that happened to me today, I was driving down the highway about 85 in a 65, up ahead I notice a tan Crown Vic sitting in the left lane, riding someone's ass, also going about 80-85. Seeing the way it was driving, I knew it was an unmarked cop car, and I hung back far enough to just keep him in sight and paced him. A few minutes later, a silver Nissan Maxima passed me on the right going about 90mph, and I watched as he obliviously drove right up to the Crown Vic, and passed him on the right at 90mph, then watched the back window of said crown Vic light up like a Christmas tree. That is a perfect example of where a radar detector wouldn't do any good, but had the guy been paying attention, he wouldn't be stuck with an expensive ticket right now.