For anyone out there looking to evaluate Cycle.js for production, I recommend looking at the source code of an open source app I'm actively building: https://github.com/staltz/manyverse I am happy with the architecture, specially how well it manages React Native's many native APIs in a well organized way.
I also need to emphasize that Cycle.js is more of an architectural framework, not much of a rendering framework, so it's not a competitor to React, you can use both together. React for rendering, and Cycle.js for architecture and orchestration.