This is a pretty good comment in that it highlights the thought processes a lot of us go through. "I can't believe ..." or "I can't imagine ...". Believe it - there are tons of people out there willing to pay for various niche things that make their lives/businesses better. I've heard the same thing about one of my own projects, LiberWriter. There's open source software that kinda/sorta does what we do, but a lot of people just want to pay someone and make the problem go away. They don't want to know HTML or how NCX files work.