It works well and is easy to use.
I'd love to explain how it works, but other manufacturers would say "Wow, why didn't I think of that?"
Here's a video of it on a Mini Cooper, which has a factory Seimans ECU with knock control function. They installed a different pulley for more boost, and added a J&S, and a Snow water/meth system.
In the first run, the water/meth is turned off. The J&S gauge lights up, showing the unit is controlling knock that was missed by the Siemans ECU.
In run two, the water/meth is turned on. As expected, there are no knock detections, showing the water/meth is doing its job, AND proving the J&S was not detecting false knock in the first run.
The J&S was more sensitive than the factory knock system, while avoiding false knock detections. All without setting up a noise table, knock amplifier gain, etc.
https://www.youtube.com/watch?v=tjA8xiPd3SU