I'm ok on speed. Not 10x or anything, but I've been writing full-stack web apps and websites from scratch for a quarter century.
The issue is getting the LLM to write _reasonably decent_ code without having to read every line and make sure it's not doing anything insane. I've tried a few different methods of prompting, but setting up a claude sub-agent that's doing TDD very explicitly and ensuring that all tests pass after every iteration has been most effective.
My first attempt was so fast, it was mind-bending. I had a "working" App and API running in about a day and a half. And then when I tried to adjust features, it would start changing things all over the place, LOTS of tests were failing, and after a couple prompts, I got to a point where the app was terribly broken. I spent about a day trying to prompt my way out of a seemingly infinite hole. I did a more thorough code review and it was a disaster: Random code styles, tons of half-written and abandoned code, tests that did nothing, //TODOs everywhere, and so, so many tweaks for backwards compatibility - which I did NOT need for a greenfield project
At that point I scrapped the project and adjusted my approach. I broke down the PRD into more thorough documentation for reference. I streamlined the CLAUDE.md files. I compiled a standard method of planning / documenting work to be done. I created sub-agents for planning and implementation. I set up the primary implementation sub-agents to split up the spec into bite-sized portions of work ("30-45 minute tasks").
Now I'm at the opposite side of the spectrum - implementation is dog slow, but I rarely have to read what was actually written. I still review the code at large after the primary tasks are finished (comparing the feature branch against main in my IDE), but for the most part I've been able to ignore the output and rely on my manual app tests and then occasionally switch models (or LLMs) and prompt for a thorough code-review.