I've built 4 pretty novel features where the LLM didn't know how to solve the problem, but with design/decision input from me was able to implement it. Between the two of us it was done, I would estimate, 10 - 20 times faster in terms of man hours than the same implementation would have taken without the use of LLMs. Like it's team level productivity from a single developer. In my case it was done infinity times faster because I just wouldn't have done these things, it would have been cost-prohibitive.