Learn it. Live it. Love it.
Strong discipline in using Styles and NOT — EVER — using what Joel is calling Local Formatting has long been the hallmark of a professional. This is why standard manuscript format specifies a plain, serif, monospaced typewriter face, certain line length and spacing rules, no double-word-spacing after periods, etc. Why? Because it makes it possible for a typesetter simply pour text into a page layout program — such as PageMaker, Ventura Publisher, QuarkXPress, or — latterly — InDesign — and get on with the job, without having to comb through the MS-becoming-a-book ONE MORE time to fix errant styles.
Now that you’re an indie, you are your own publisher. This also means you are your own typesetter and book designer. There are major and minor arcana of book design, some of which you must learn — fail at your peril — and some you may ignore. But know this: no matter which class an item falls into, following a disciplined workflow — of which standard MS format and the use of Named Styles are the first steps — will help to ensure that your output is professional in appearance and function.
Why does it matter? Does the appearance of your work matter? Does neatness count? Do you even have to ask? Take a samizdat book that’s typeset in Courier, with uneven line spacing, pages all wibberty-jobberty, inconsistent styling of various page elements. Compare it to a book that’s professional in design and appearance. Which are you more likely to plunk down good money for? Or, having bought both, from which author are you likely to buy a second book?
Yes, poseurs and hacks like to poke fun at “slick” production values. But, as a professional, allow me to assure you, those production values exist for a very good reason. And, if you want your book to look like samizdat, or a Xeroxed MS, passed form hand-to-hand in the underground, well, that’s a style, too, and it takes a great deal more artifice to produce than the “slick” standard production values take.
But, if you want to make money — or even your living — as a self-published writer, then it behooves you to follow a disciplined workflow that delivers consistently professional results to your ultime customers — the readers.