I thought I would put my thoughts up front, as its a pain in the butt scrolling through so many replies.
I just did a week long trip cross country from Denver, CO where I live, to NYC, and back in my Nissan Altima, while towing a trailer with a motorcycle on it, both ways ( a small dirt bike to NYC, and an older Kawasaki Vulcan on the way back).
I always drive with my V1 mounted on my windshield, as it allows me another piece of driving data as I coast along the I-70 and I-80 corridors.
What I know, is that here in Denver, all the local police departments and State Troopers all use Ka and LIDAR to patrol the highways. Its very rare to ever see a police car running K or X band out here.
On my cross country trip, I was surprised how many police cars were using K and X band. The vast majority were still using Ka, and I think there were less than 6 instances were it indicated LIDAR was in use, and I believe that at least 3 of those were caused by the high end car cruise control systems.
In fact, one specific time I had K band go nuts, was when I was in New Jersey, and approaching a series on entrance and exit ramps to the highway. I actively switched from the second to left lane to the second to right lane, and dropped off about 5 mph, as I watched the signal strength grow as I got closer to one specific entrance ramp, all while having cars whip around me, passing in the two left lanes.
As I passed the bridge, the K band strength maxxed out, and I was then able to see the NJ State Trooper halfway up the entrance ramp, sitting there, tagging everything that drove past. That very moment was when he pulled into the entrance lane, and joined into the flow of traffic, and merged onto the highway in the left lane.
I watched him as he pulled past me about 1/3 a mile later, and settled on a black Lexus ES300 that was in the left lane, and pulled over the lady who was driving.
If she had any radar detector in her car at all, she would have had warning, and if she paid attention to it, she wouldn't have gotten a ticket that day.
There were also many many police cars that I passed that I didn't get any warning about, as they most likely had instant ons of some variety or another, and when they see something that they think is worth tagging, then they let you have it. By then, its way too late.
I also noticed a situations where there was one police car on the side of the road using an always on, in plain site, and when you got past him, and thought it was safe, around the next hill, curve, or entrance ramp, there would be another (or several) police cars that were silent, with instant ons, just waiting for those people who thought it was safe, and started speeding back up.
But yes, the arrows come in handy when you pass a silent police car on the side of the road, and then a little further up the road, you see a medium strength arrow pointing behind you. That lets you know you picked up a tail, and you should take it easy for a while.
Also, in Kansas and Colorado, the Troopers love to drive the speed limit in the left lane of the highway, and tag the cars going in the opposite direction in unmarked police cars. This is a very handy time to have the arrows, as you will be able to identify which car is the source of the signal, and can see if it turns around, and trails behind you for a while.
BC.