where I live instant on and "laser" (lidar) are the norm for speed traps but many still have the older bands mounted to the A and C pillars of their cruisers and about half of them leave it on as they go down the road. so it will notify you that they are on the road and near by but wont necessarily save you a speeding ticket, if you are doing other things that only seeing you do it will get you stopped then it can help. (wheelies, lane-splitting where it isn't ok, stoppies etc)
knowing this I have found trapster to be the most useful tool, especially with them parking on the e-way on ramps getting speed readings from behind you less than 200 feet away. barriers block much of the stray wavelengths (there isn't a lot to start with from that close up)
in rural areas trapster is less effective because people are not there to upload the trap locations. but in these areas the budgets are lower so the radar guns are lower tech giving your detector an advantage.
just my .02