I have a 8500x50 and love it. I bought it when I was in college out in Western NY, and making many trips to see the gf in Albany, and or home to Maine. Seeing as the NY Thruway is mobbed with troopers it seemed like a good decision. And it was. I was able to up my cruising speed 10mph. The troopers in NY run Ka and leave it on all the time. So it's easy to pick up. Although they did hit me with lidar a few times, luckily I slowed down due to traffic when I was ...
Since you're in the area I'll give ya what I've noticed around here, maybe some other locals can chime in and help.
MA - I rarely pick up anything from them, and see them even less. They're mostly MIA on 93/95 north (at least on my stretch). But when I drive 90 I normally see them pacing people.
NH - I rarely pick them up, not sure what they're using. I've seen them pacing people as well. They also will use aircraft to clock ya. I generally don't speed to heavily in NH, those buggers are tricky... that and the damn 55mph zone ...
ME - Normally don't see them too often either, but when you do they're usually sitting in the center with their gun left on, the 8500 has no trouble letting me know ahead of time.
But to echo what Mugs said, a radar detector is not a silver bullet. If you're driving like an idiot there is nothing it can do. I personally don't drive crazy, just quickly, so it works out well for me. I don't know how Spidey gets away with 90mph plus, even with a detector that's fast, as I'm pretty sure the troopers would notice me lighting up the brakes to get down to legal limits, as coasting down from those speeds takes forever. It obviously depends on how strong the reading is and how fast I'm going, but I normally don't like to take that chance.
My radar detector has paid for itself though. Now I use it just because I'm used to it. You can also hardwire it in, makes for a much cleaner look.