I bought this disc several years ago. It does work but not on all CDs it seems. I did a blind test with my son-in-law with a certain Red Hot Chili Peppers cd and he, and I, could hear a difference in tightness of bass and clarity of sound-stage.
Not all music styles seem to benefit from the disc, at least not audibly. I think how revealing the equipment is also determines how well this disc works. I think it offers good value for a small incremental improvement.