I use it fairly regularly if I’m getting out on the interstate. Not necessarily for the position of LEOs - I generally do not speed. However, they can cause others to slam on their brakes or do other stupid stuff. The app also lets you report traffic backups, road hazards, etc. It is also fairly accurate at predicting arrival times and I like the 3D moving map display better than my dedicated Garmin.
I downloaded Waze and used it on my 30+ mile trip to work today.
My preferred method of avoiding trouble with cops is to follow the rules.
I drive the speed limit, accelerate smoothly, stay out of other divers’ way, stop completely at stops, and anticipate/avoid trouble spots.
On my way to work, I got 4 cops alerts, and there were no cops to be seen.
I also got various useless alerts for cars on the shoulder and pot holes...none was helpful.