It helps if you've already got a decent codebase built in it with standard patterns covered.
Most of my sites start as a copy of an existing site as if it's a framework and then I clear out the product and just use the shell to build from. The result is that the agent is pretty good at replicating existing patterns and if I ever hit something similar I can just tell it to look up prior art in other projects.
The initial learning curve was definitely there, and I still hit edge cases as mentioned above. I just don't have to resolve the "how do I handle auth + middlewre + htmx targeting for a form in an admin screen (for a random example).