His products have received excellent reviews for years in many publications. People are obviously buying the products or his company would not still be around. Plus, other manufacturers have licensed various technologies from him. Just like cables, they work well in some systems, not in others.
Consider that the explanations as to why various cables work range from fairly rational to completely nuts and, given the huge range of products and approaches what truly works remains quite mysterious. Yet, many pay hundreds and thousands of dollars for a single meter pair because they find they work - regardless of the explanation. Non-audiophiles find this absolutely ridiculous which, of course, it is.