Peter - as long as its legal - there's nothing inherently wrong with using a radar detector. It doesn't even mean you're speeding. A friend of mine keeps one (out of sight) just so he can be extra aware when police are around. He almost always drives the speed limit, and is a good driver. Unfortunately for him there are some places in the US where you can still get a DWB, despite being well educated, well spoken, and driving a nice, but not ostentatious car. Assuming a radar detector's only purpose is to dodge speeding tickets is just plain silly.
There's a comedian who says that everyone slower than you is an idiot, and everyone faster is a maniac. You admitted that you speed, 68 in a 60 on the highway. Give all the reasons you want for why thats okay, but 70 in a 60 isn't - they're all bologna. Fact is, people will generally drive at whatever speed they feel is safe. Many of the speed limits in the US were set during the oil crisis in the 70s; others are arbitrarily set by a municipality looking to use its police force to bring in additional revenue. If you're not driving dangerously, there's no reason to get pulled over. A radar detector just might alert you that the local constabulary is around, and to switch to "follow the rules" instead of "drive safely."