I've been using an old radar detector I bought from Costco in 2005, which so far has been adequate. That is, until it's sensitivity went south a couple of days ago - though I had not 'detected' it until I got snagged going through the Utah open desert at 96. The detector went off alright, but only when the Highway Patrol cruiser was on my bumper with red lights on.
I knew it had been acting squirrely just a day before. I went through a radar zone in California on my way to Salt Lake and noticed that it barely went off, and I had a CHP guy with hand-held radar gun pointed right at me - except that he was on the other side of the freeway on an embankment and was tracking cars in the opposite direction.
Anyway - I'm fishing for a new one which I need ASAP since I drive through California - Nevada and Utah on a regular basis.