Jekyll utilizes Markdown and RST formats. This will come in handy when you take all your blog posts and make them into a book.
Backups (Via GitHub)
Using GitHub for managing your jekyll blog is only natural. It's where Jekyll came from after all (see GitPages). You can even host your blog straight off of GitPages.
Jekyll renders your site into static HTML pages. This site (static) loads much much faster then my previous site (dynamic). You also get the benefit of not having to hassle with a database and can run on any HTTP Server since its all just HTML.
Jekyll is just plain cool, fun and super hackable. I'm constantly being suprised with what people are doing with Jekyll (3N).
Start hacking on it and see what you come up with.