This question has been going round and round in my head since I read the release notes (and other related hype) around React 0.14 - I'm a big fan of React and I think that stateless components (https://facebook.github.io/react/blog/2015/09/10/react-v0.14-rc1.html#stateless-function-components) are an excellent idea, both for the ease of writing such components and for expressing in code the intention that these components should be "pure" in terms of rendering consistently for the same props data.
I've been trying to find out more information about this but haven't got anywhere. I can't envisage what performance improvements could be made around stateless components without presuming that props data will consist of immutable types.. maybe some preliminary analysis of non-immutable props types to try to guess whether "props" and "nextProps" represent the same data?
I just wondered if anyone had any inside information or some otherwise enlightening insights onto this. If React did start demanding that props types be "fully immutable" (allow reference equality comparisons to confirm that data has not changed) then I think that would be a great step forward, but it could also be a big change.