I wrote a long Reddit comment a while back that describes the reasons why I advise that people _not_ use Immutable.js [0].

As a quick summary:

- It doesn't magically improve perf the way some people think it will. It does make easier to use the standard shallow equality implementation of `shouldComponentUpdate`, and can be faster at copying/updating very large objects. However, many people use `toJS()` to extract values, and that is absolutely bad for perf (especially if you call it in `mapState`).

- You either have to use its API everywhere in your codebase, or spend a lot of time encapsulating it to keep your components unaware of its existence.

- It can be harder to debug the contents of the objects.

I'm not sure about specific downsides for using Seamless-Immutable.

My React/Redux links list has a section of articles that discuss the pros and cons of using Immutable.js for performance [1]. I've also got a section on use of immutable data in general [2], including some articles that talk about how to actually use Immutable.js in your app, and articles on using plain JS data immutably.

[0] https://www.reddit.com/r/javascript/comments/4rcqpx/dan_abra...

[1] https://github.com/markerikson/react-redux-links/blob/master...

[2] https://github.com/markerikson/react-redux-links/blob/master...