For experienced devs who already has solid understanding of the codebase they are working on, the potential upside of using AI is rather small. But if jumping into a new codebases, AI (with codebase context) can be used as a semantic search tool, or simply speed up the process of codebase understanding. And when it suggests code, it can surface patterns/conventions that were not documented. Need to be careful though, because it can repeat bad code too.
Disclosure: I'm building EasyCode, a context aware coding assistant.