By the time the radar detector warns you it's too late since they already have your speed. Unless they happen to check a car right in front of you first but then if you slam on your brakes you're getting stopped anyways. And you made a valid point you can get cited for having one in VA and DC but they are legal everywhere else. Personally I will never get one because they aren't very effective and if a cop sees one the warning you were about to get just went to a ticket.