We use them all the time,nearly every job. They help tremendously especially on multifloor losses, roof leaks or anytime it's not obvious where the water came from.
It also helps sell the job, when you can visibly show them the wet affected areas that you cannot see with the naked eye.
We've had them for years, we have 3-of them, spent over $40,000.00 on them originally, of course now you can buy them for a third of that.