I am in the market for one and wanted people's input on what they use or have used and if they would recommend it or not. My boss had a Valentine V1 and said it worked good, but he use's the iRadar now with no complaints. I don't mind spending the money on a good unit just don't want to purchase one I will regret.
If you're going to speed, speed. Nothing gives you away faster than slamming on your brakes once that detector lights up.
I generally keep my car within 5 over and I've yet to get a ticket. Don't be a douche about it, don't weave in and out of traffic, stay out of the left lane unless passing, and don't speed in neighborhoods or on city streets. If it's raining/snowing/foggy, drive the speed limit or lower, and watch for plain black impalas and chargers. We have a bunch of unmarked explorers up here too, but the extra LED's around the license plate give them away as well as the illegal super dark tint.
I wouldn't waste my money on a radar detector. How fast do you really want to go anyway? Do the math on any given distance. Say you're doing 75mph on a 150 mile trip. If the speed limit is 70, that saves you less than two minutes. Doing 80 saves you 10 minutes over doing 70, but that's not that much time. If you're going a much shorter distance, say 15 miles, you're going to spend 13 minutes at 70, 12 at 75, and 11 minutes at 80... Not enough difference to worry about.