honestly, my biggest lesson is to stop treating it like a ghostwriter. It's a terrible storyteller if you just ask for a chapter. Where it shines is as a hyperactive, infinitely patient brainstorming partner. I'll get stuck on a scene—say, a tense negotiation in a fantasy tavern. I'll feed the AI the characters, their goals, and the setting, and then prompt it to generate ten different ways the conversation could go wrong. Nine will be unusable clichés, but that tenth one might have a character accidentally insult the other's obscure cultural tradition, sparking a whole new subplot I hadn't considered. That's the gold.
The drafting speed comes from using it to bypass the 'blank page terror' for non-critical sections. Need to describe a city your hero is passing through quickly? Have the AI generate three sensory-rich paragraphs, then you rewrite one sentence to include the specific, rusty weathervane that matters later. It's like having a clumsy assistant who vomits out raw material; your job as the author is to curate, refine, and inject soul. I'd never let it write dialogue I care about, but for procedural stuff—a coroner's report, a dry historical preamble a character is reading—it can save hours.
You have to be ruthless, though. The prose it generates has a certain flat, 'competent' rhythm that can infect your own voice if you're not careful. I always paste its output into a different font so it looks alien, then rewrite it in my own words, keeping maybe a nice turn of phrase or an interesting detail. The goal isn't to have the AI write your book, but to use it to constantly generate branches on your decision tree so you never sit there paralyzed, staring at the cursor.