We were discussing this some in our SN weekly meeting yesterday. Beyond the obvious AI spam, I think even functional, error-free AI code can grind a team down. The main problem I'm seeing is that AI code is harder to read because, aside from the excessive line count, it wasn't produced by nor, often, read by a human. It threatens human maintainability of a code base, which is maybe worth the tradeoff if everything will eventually be written by AI, but in the meantime it tends to make complex, non-linear, abstraction necessitating code even hard to extend. It's kind of like adding a team member that insists on abstracting things before abstraction is required - it obscures things more than needs to.
To the upside, earnest contributors do read the AI code and make sure it makes sense, and AI lowers the barrier to entry for them. But earnest contributors of this kind, especially when you're incentivizing contributions like we do, are going to be in the minority.