Sorry to resurrect this oldish thread, but I thought I'd throw my two cents in on the less-expensive radar detectors, based on a recent trip I took with one.
I'd like to preface this by saying that I pretty much drive the speed limit (+ 5 MPH), and that I picked up the cheapo RD more for entertainment reasons on long trips than anything else. I do have a concern of the automatic camera / radar units that are used in MD and other states--IMHO they are just revenue generators and do nothing to enhance safety. I've never been tagged by one and I don't want to.
That being said, I'm a retired LEO and I know how the system works and I've logged more hours than I cared to using speed enforcement devices. I wasn't an ardent traffic guy, but I wrote my share of tickets and gave way more warnings than tickets. If I wrote a speeding ticket, you had it coming. I also understand the limitations of speed-control radar units and how they're used.
The RD I bought was a Whistler Z-11R+ (
https://whistlergroup.com/products/z-11r-laser-radar-detector ). I just returned from a 700+ mile trip from PA to NY and return to PA, mostly on rural, divided highways. Based on reviews on some of the RD forums I was expecting this unit to be practically unusable. In reality, I thought it worked quite well. I quickly learned that most X/K-band alerts were blind-spot detectors on other cars, but the filtering built into this unit eliminated most of them. I'd (at most) get a couple false alerts per hour. When I got a Ka-band alert, there was no doubt that it was from a police radar unit--and in many cases I'd start getting intermittent warnings quite far away. In the cities / small towns we went through, I'd get an small increase in false alerts, but I left the unit in highway mode anyway. In one small town, I got a Ka-band alert as I approached an intersection, which turned out to be a police unit coming from the street to my left--I had about a 30-second warning before he went by. In another instance, there was a NY Trooper in a cross-over running instant-on radar behind some trees--I started receiving alerts for him about 1/2 mile away as he lit up vehicles ahead of me. I didn't get a single laser alert during this trip. NOTE: I used default option settings and didn't turn on VG-2 cloaking, POP etc. Turning those options on seemed to increase false alerts. As for comparing the Whistler against more-expensive units, I'm now wondering how a Valentine or Escort could have given me better performance--are the critics just trying to justify spending $300+ for their RD?
I can't comment on longevity for the Whistler, but so far I think it works well for the money. I'm not condoning use of a RD for felony-level speeding, but they do increase awareness in a world where driver awareness is sorely lacking.