1) Is this cross platform or are you still going to have separate code bases for the UIs of iOS and Android? Looking at the code in the demo there are components like View, Text and Image. As basic as they are, are they the same on iOS and Android (same behaviour, same arguments)? It was pretty clear from the first minutes of the video that View is build on top of the native view of iOS (he showed the objC code). Is that React code building for Android?
2) I guess that one must still be proficient in iOS and Android, unless they make the monumental job of rewriting all the iOS and Android documentation for the React components they implemented. I expect to have to reference the native docs to understand the meaning of the arguments and do the job of mapping React to native. That has always been a pain point in many UI abstraction layers.