I like Latex (Math/CS background), but I would definitely like to try some alternatives (like Asciidoc discussed in https://news.ycombinator.com/item?id=8509062 ). The problem is I never can tell which Markdown/Docbook inspired systems actually have working implementations and which ones are hot air. I don't want to end up with a big SGML mess that I can't do anything with or have to edit CSS just to render a book in…
I'm currently writing a book in asciidoc which produces output in all your mentioned formats and includes footnotes, endnotes, call-outs, code listings, index etc. However, whilst I write almost exclusively in asciidoc, a lot of the styling etc is done by the publisher's docbook workflow.