I love/hate my radar. If I'm cruising around an area with a lot of stores I just shut it off because it gets fukn annoying. Although it CAN save you some money, DONT PUT ALL YOUR FAITH IN IT!!!!!
Most POS pigs use the "instant on" type radar, so you cant pick them up until its too late. if theres a few other cars in front of you, and they get clocked, you'll pick up the signal, but only for a second or two, so BE CAREFUL.
I've only gotten 1 ticket since I bought my detector 2 years ago. Although I lost 250 bucks (83 in a 65), it has saved me at least 20 times, so probably in the neighborhood of about 5k lol. Not only good for speeding, but also burn cruising, booze cruising, you know, whatever you're into haha