I did a decent 200mi trip today with XTR-690 and V1 mounted high on our family minivan (which is, btw, one of the perfect unassuming vehicles!)
At any rate, first encounter was an interesting CO Ka with Michigan State Police. The cruise had already pulled a car over but left his radar on. It was a relatively straight road but pretty hilly. I got my initial Ka alert after I already saw the cruiser's strobe lights, about 1.5mi away. It stayed weak at 1 to 2 bars. Initially, I was quite disappointed at this performance, until I got near the kill zone. It turns out the cruiser was pulled over, facing diagonally with respect to the road, on a slight hill, and the ramp-up on that final hill approaching him was exponential. I doubled back 2 miles to try the same approach with the XTR-690 on and V1 off, and the it only alerted one blip in the 1mi leading up to the kill zone, stayed silent otherwise. It only began alerting again on the final hill approach, freaking out for the 5 seconds or so until the cruiser was in plain sight.
This is the kind of encounter that answers why an ultra-sensitive detector is worth it. This is not saying the XTR-690 performed below-par -- remember the V1 was only alerting at one dot until the final approach, which is below the sensitivity level of the XTR-690. In this specific case, the extra sensitivity of the V1 made the difference between a kill or no-kill.
On the way back, I was bored and drove with both detectors on, separated a windshield's distance apart. As I said, I was feeling bored and wasn't speeding, so I decided to experiment a bit. We encountered a moving Ka MSP unit on I-94, which was also quite interesting. The V1 started reporting Ka ahead with linear ramp-up a minute before the encounter. 10 seconds later, the XTR-690 chimed in with its female "Ka band" voice. When the XTR-690 alerts, it seems to leak Ka, which caused the V1 to bogey-lock to 2 bogeys, one ahead, one behind. In this case, I was very satisfied with the XTR-690's performance. It alerted when the V1 was at Ka 3-dots or so, which is from my experience typical of the REV C's performance.
I did run the V1 with POP ON the whole time. Overall I managed to get two junk-outs (and I was quite excited to hear the tone) and one unexplainable Ka bogey that came in at strength 3 and went away. On a 200mi drive packed with other cars, I think that's pretty respectable POP mode filtering.
Overall it was a fun drive, both demonstrating the competency of the XTR-690 and showing a reason why a higher sensitivity detector can be so advantageous.