My radar detector that I paid a couple bucks for got road tested recently. We went down I-20 to Vicksburg then down and across Louisiana to Tejas. After spending several days in Tejas, we headed for home by way of Mobile, AL. Then finally from Mobile to Hot-Lanta. The unit seemed to work, got alerts on all the bands, it helped us to see the cops sooner than we would have without it. We don't usually drive that fast that the detector would be necessary, but it still helps.
It worked fine out on the highway, in town it gave a number of false alarms because of automatic door openers even when set on 'City'. All in all I'm pleased with it and considering what I paid for it, I'm real happy.