When I look through the listings here, I find item volumes difficult to assess since I don't have knowledge of the number of total units out there. I suspect PS Audio has sold a lot of these. Though there have been a number of postings here expressing various concerns about the product, I have a P300 and think it works as advertised. The multiwave included--though its impact is marginal compared with the other benefits.
That said, I may be selling mine in the near future. The P300 works great for my CDP and preamp but can't run all my gear. I suspect that the greatest improvement comes from running these two components from a Power Plant. Power quality where I live is a big issue though so I am upgrading to a more comprehesive solution. From the commentary in many of the classifieds, it appears others are doing this as well. --Scott