> I suppose I could also sit there and spend 9 hours writing out a "perfect spec" but we've already tried that with waterfall development!

And a perfect (or near-perfect) spec is actual source code. And that's where I see myself with LLMs. They are great about generating source code. They are terrible at writing well-specified software, and so they need a lot of context: docs, plans, existing source code, existing templates or examples. And even then, they still need a lot of guidance.