I love Ember - and one of the best things about it is its emphasis on convention over configuration. React is the exact opposite. While it's an amazing library, it only makes up one part of a front-end stack, which causes everyone to waste tons of time deciding on what the other parts should be.
A set of sane, accepted defaults would help the community tremendously. Personally, I'm hopeful that that's what React/Redux/Webpack turns out to be.