Well it was my return trip to school and I decided for the fun of it, I'd let my XRS-9400 ride my windshield.
Encounter 1: constant-on Ka band from SUV cruiser, onbound across a small median strip. I already visually identified the SUV and estimate it was only like 150ft away when I got my first beep-beep Ka alert, and then the detector went silent for the rest of the encounter. Totally useless detection -- I'm sure he would've had my speed by then, not to mention it was a 1-second alert that could easily be taken as one of the million falses the stupid thing makes.
Encounter 2: K-band speed sign around a 180-degree turn. When you come out of the turn, you are at point-blank (~100ft) range from the sign. I saw the speed on the sign (and it was surely my speed) before the thing went off.
By contrast, both my XTR-690 and 1793SE would've been able to provide ample reaction time to these two encounters (though the 1793SE might be a bit tight on oncoming Ka) as I've experienced these encounters many times before. However, had I been the target of a real cop in either case, this detector would've costed me a ticket.