It's worth mentioning that much of the code that integrates with React internals is based on the work in react-art: https://github.com/reactjs/react-art
This is the same technique used by Netflix for their React-based television UI.
Custom fonts are supported on flipboard.com using the same rendering engine. It was just a matter of time to extract the Flipboard specific bits out. This is coming soon.
React Canvas author here. I outlined some of the reasons why it is not always the right answer: http://engineering.flipboard.com/2015/02/mobile-web/#Practic... On Flipboard we use DOM where appropriate for text input and areas of the application where performance is less critical.
You are correct that the DOM just works. But we need a better option on the web in order to achieve the kinds of experiences that people have come to expect from native applications. The hope is that by pushing the browser beyond its limits that we can make progress in this area.
This is the same technique used by Netflix for their React-based television UI.
https://www.youtube.com/watch?v=eNC0mRYGWgc