The only benefit I can think of is prevention of [accidental?] modification of `state` within your selectPropsFromState functions or within rendering code itself. Which is something you should never, ever do anyway, and the mistake should be quite obvious given redux's suggested structure. Given ImmutableJS also has a performance overhead in ES5, I'd definitely agree with you.

The biggest reason we adopted Immutable.js is that it allows us to use PureRenderMixin (or, to make some situations even simpler, https://github.com/jurassix/react-immutable-render-mixin ) for all our components. This gives a great performance boost, without having to think how to design a specific shouldComponentUpdate for each expensive component.

This is especially important with Redux if you connect your store to one controller-view which then passes the props down to a big tree of components (which should be the standard way to do things with both Flux and Redux).