I think it's also interesting to note that sometimes when choosing immutability as the default, which gives a slight performance penalty for basic operations co

I think it's also interesting to note that sometimes when choosing immutability as the default, which gives a slight performance penalty for basic operations compared to doing normal mutation, you end up being able to save lots of performance on a larger level. React wrappers in ClojureScript, such as Om, are a good example of this - since data is immutable, shouldComponentUpdate is automatically and trivially implemented for you, leading to oftentimes better performance than straight React. I reckon this would also be the case with the lock-free code you write in Clojure, etc.