I find that it's relative to the amount of planning time you spend... I feel like I've gotten around 5x the output while using Claude Code w/ Opus over what I will get done myself... That said, I'm probably spending about 3x as much time planning as I would when just straight coding for/by myself. And that's generally the difference.

I can use the agent to scaffold a lot of test/demo frameworks around the pieces I'm working on pretty cleanly and have the agent fill in. I still spend a lot of time validating the tests and the code being completed though.

The errors I tend to get from the agent are roughly similar to what I might see from a developer/team that works remotely... you still need to verify. The difference is the turn around seems to be minutes over days. You're also able to observe over simply review... When I see a bad path, I can usually abort/cancel, revert back to the last commit and try again with more planning.