PDG,
I feel very frustrated for you, that you do such excellent work that obviously hundreds of site visitors are enjoying and there is only a handful of us who acknowledge your very fine efforts. I would encourage you to continue your work despite the apparent lack of appreciation from people using your downloads.
I would submit to you sir that the very fact that your downloads are being used in great numbers is in and of itself a great compliment. There are many who are enjoying your units and there will be many in the future. Keep in mind that marketing statistics worldwide indicate that the overwhelming majority of any sample population will not take the time to write a letter of thanks or appreciation or even to fill out a brief surveys. In fact marketing statistics in the English-speaking world indicate that only about 1/10 of 1% of the sample population will actually respond with any level of feedback.