The Valentine 1 doesn't help if the cop is pacing you.

Yep. Everything I've read on the topic of speeding tickets drives home the concept that a radar detector is only one tool, and you've got to know and be prepared for the other possible methods they use to clock you. Here in CA, pacing and KA-band radar are the two favorite methods. And unlike some radar tickets, a pacing is ironclad in court.

Even before I got the radar detector, I always would constantly maintain a visual scan for highway patrol, including scanning for unmarked cars, which isn't easy. As I approach groups of cars from behind, I'm making a mental checklist of the vehicle types, based on what I know is/isn't used as unmarked HP vehicles. If I'm unsure about any one of them, I slow down as I approach.

As I get closer to them, I start using various identifying characteristics to rule out the "unsure" vehicles. Sometimes it's very tough, requiring that I approach closely enough to see if there are DMV tags on the license plate corners (government vehicles are exempt from needing the tags).