I have heard a lot of people that use the Demagic and most of them is positive, but the only complaint is that the effect doesn't last that long, so you have to do it regularly.
Densen has a pragmatic approach to making audio equipment and the Demagic is made because they believe that it can improve the sound.
I have had several amps and cd players from Densen, and they make some really nice equipment, with a great sound.