It all depends on how you use it. I've been using a Valentine 1 for over 20 years and and have 3 tickets in that span. 2 were on a motorcycle where I didn't have it with me, and the other was VASCAR (no radar zone - PA is weird with radar restrictions...). On the interstate, my strategy is to find some other idiot who wants to tempt fate and then tail him about a quarter mile back. That should give me enough time to react, even in the case of instant-on Ka (or in some cases laser). If you're fool enough to lead that pack at break neck speeds, eventually your number will come up regardless of how good your detector is.
The reality is that the police can write as many tickets as they want, all day long, and all the really need is VASCAR or K-band. They will get more than their fair share of stupid drivers with even the most mundane methods. Plus, Ka and Laser actually require WORK. The bands are narrow, and you generally have to point and shoot, and not suck. It's a skill, and who really wants to be bothered with that? I used to think the PA State Troopers were neanderthals the way they standardized on old fashioned K-band, but now I see the genius of it. Sit back in the cruiser, relax, and wait for the idiots to fly by. Even better, just compute times between toll booths on toll roads and hand out the tickets at your leisure. I'm pretty sure you could train a monkey to do that job. Either way, you can still rung up plenty of numbers without breaking the bank.
Aircraft enforcement is a sad joke. Any public official who tries to justify the budget for such and operation should be strung up at city hall IMO. How much does it cost to fly a plane per hour? A helicopter? How many tickets do you need to write to cover that absurdity???
Please don't misunderstand my rant. Cops do a hard, dangerous job that I don't have the guts or patience to do. Traffic enforcement, unfortunately, is a necessary evil - it's a part of the job and they are required to do it. It's not even safe - we've all seen the videos of these guys getting mowed down during a "routine" stop by some clueless, half baked imbecile. That said, from a revenue perspective, it's a game. Play smart, and if you get caught, it pays to play nice.