Detectors are not a waste of money but they are not going to.....all by themselves....save you from getting nabbed.
Laser spreads with distance. The good news with this is that when the guy in front of you is getting zapped, your laser detector will still go off. I've had this happen many times. But I tend to drive in the right lane, since most of Eastern Mass feels that they must be in at least the middle lane. So while the guy in the middle is getting pulled over for 72mph, I'm hearing the laser detector going off and slowing down from 75.
Laser is no more deadly than instant on or aircraft detection. NH does random arial detection with the pack of state police cars just waiting for you. Has been going on for at least 30 years. Instant on is easier because they can "shoot" one guy and you hear the strong hit, then it's off. Very different from a random electric door proximity sensor.
I like my Valentines because they tell me the direction and number of hits. Helps in places with normal ambient hits. If I'm going north into Nashua on 3, I know I'm getting an ambient hit. If I see a second hit ahead, I know that they're waiting around the corner (a common place where they wait). Same on the turnpike east, next to the right turn guard rail after exit 12. Be aware. But a waste of money? No.....can't agree with that at all.