I'm currently using a BEL 980 - works pretty good.
However, the police here in upstate NY use tactics that cut down on a any radar detector's efficiency.
The police here mostly use laser and Ka instant on. They like to park just past overhead bridges with laser or Ka band instant on radar and shoot perpendicular to the traffic flow. In either case, there is minimal reflection back to your detector from them shooting the car ahead of you. In other words, if your detector goes off in such a situation, it usually means that they are shooting YOU. You will almost certainly be clocked by the radar or laser in the officer's car with minimal warning. Slow down in places like this. Usually if you are going more than 15 mph over the speed limit in a situation like the above, all your radar detector going off means is that you are going to get a ticket, in most cases.
They also use VASCAR. This is basically a fancy stop watch system. They usually park on a hill and start the clock as your nose crosses the first timing mark on the road, and then stop it as your tail crosses the other timing mark down the road. This usually gives you a slower reading than you are actually doing, since this method gives you the length of your car to some what make up for the officer's reaction time. They know how far apart the timing marks are, and a computer calculates how fast you are going from the distance/time relationship. NO radar detector will detect VASCAR, since it is merely a visual reading by the officer. Look out for white lines across the highway in places that seem to have no reason to have them.
In the above cases, there is usually a passle of police just up the road waiting for the officer who clocked you to radio them a description of your vehicle and your speed. They will then issue you your ticket and say "Have a nice day!".
Cheers!
Dave