It's one of the ideas for shouldComponentUpdate that I wrote about here, but it's not described in a lot of detail:

http://guscost.com/2015/05/27/react-js-and-flux-ideas-for-pr...

One of these days I'll put up another piece on Flux/React, and an example application to demonstrate an approach that doesn't have a lot of dependencies (not even ES6, for example).

Also I have not run into any pitfalls using ImmutableJS yet apart from the extra overhead, so thanks for the heads up.