I am a RD-2 owner for two years. In my highly revealing system, the improvement with every disc - better and more bass, better soundstaging, less harsh sound, better defined voices - is often so startingly that a high end-loving friend of mine, who regularly comes over to listen to my system, asked me if I had switched to another, much better DAC, when I took out a disc I had just played, treated it with the Furutech (without him noticing), and played it again.
Why does it work? Because CDs are not made of plastic alone, but contain parts of metal. Anyone interested in how and why it works may take a look at US patent 6058078 of May 2, 2000.