Here's a library that integrates the two https://github.com/react-d3-library/react-d3-library

That's actually a pretty reasonable idea, considering that we have several fairly different renderers for React already: DOM, Native and Three.js (http://izzimach.github.io/demos/react-three-interactive/inde...).

The big question is, should it render down to D3's API, or should it implement it in a way that is idiomatic to React, like this demo?

From the site: This is not a library, but rather a demonstration that it's possible (and preferable) to use React instead of the core of d3.