I've heard the Qol on several different systems now, including Maggie 3.6, Apogees, small Gallo's and Pipedreams.
I can say, in general, I didn't like what it did to the panel speakers. They are already capable of producing wide open sound. The QOL was a bit too much of a good thing, and you can achieve the same presentation on these with proper setup and room treatment.
However, on cone speakers the QOL was very nice indeed. Those little Gallo's sounded like floorstanders and filled the room. On the Pipedreams it made the presentation far more expansive.
So overall, YMMV depending on the type of speaker system you are trying this on. And yes, the price point of this puts it out of reach for many people, and no I have no idea how it works except that it must play with phase. That means it is probably not a device for the purist audiophile, but more for someone who just wants things to sound good to their ears.