Anyone use it or played around with it?

Audi s4 owners use it a lot.
If you check out Audizine and look up B8 S4 forum there's a lot of information about it.

Been using a devils own kit on the last 2cars , I just have a trigger from the ecu based on boost and air inlet temp and run home mixed de mineralised water with 30% meth content so it doesn’t make a big difference to afr just helps pull heat out and adds a little fuel content

Froggy - do you have any failsafe system built in that lowers boost or retards the ignition in the event of a blocked nozzle or running out of meth/water mix?

No , I spray a single jet triggered on boost and inlet temp . I clean the filter in the jet every couple of months and run a 2 gallon tank with a 400cc jet . It’s purely for safety with my 1uz v8 being 10.4-1 compression and pretty much never used any on the road just for track use . My pump is 6 yrs old and never given me any trouble .

As Dave above, i have Devils Own system on my kitten, controlled by the ecu by tps, air temp, map, rpm (you don't really need all those parameters for control). I'm lazy though and use their ready mix which is a 50/50 mix. Definitely makes a difference on air temps and reduces the chance of det if your pushing things a bit (high comp/too much boost/heat soak etc etc). Never had an issue with the pump/nozzles, but the 50/50 mix does shift the afr's a little richer by about 0.3 in my case.

Ian