Sounds like the general "LLMs are net useful or not" sentiment here too. Personally Rust+LLMs work great, and workflow is rapid for as long as you can get the LLM to run one command to say "good or bad" without too much manually work, then it can iterate until it all works. Standard advice for prompting like "Don't make tests pass by changing assertions" tends to make the experience better too, but that's not Rust specific either.