I've bought quite a few books from Delphi, many with the copyright restricted contents (US). Given the low prices of their volumes I tend to wait until there are 5-10 books I want to buy, so I was waiting for a few more books to be added to Series Three before I made my next purchase. Now I'll have to make a decision about whether to continue purchasing from them.
Delphi made a commitment to provide free lifetime updates and are now reneging on that commitment unless we can prove we bought the books (I don't keep receipts, paper or otherwise, once I am satisfied with a product). I contrast that with the very costly and error-prone efforts being made by Barnes & Noble to honor the purchases made on both Fictionwise and eReader.com. I will admit there have been all kinds of problems, but they are at least trying to make good ... and they aren't asking us to provide proof that we bought the books.
I guess I'll have to decide whether or not I still value the service/products they provide at such a low price given that their guarantee for free future updates isn't worth even the paper it isn't written on. I suspect that decision will be made on a case-by-case basis. For certain I will no longer buy volumes that are missing significant works of an author until after those works have been added.