Immutable data structures are harder to implement yourself, not to reason about.
Anyone who has spend a few days with Clojure realize how much more easier it is to reason about them and to work with them.
Immutable data structures combined the software transactional memory that Clojure provides are a godsend.
In a lot of case they're also much faster then the good old copy-on-write and because they're immutable you have lockless concurrency. This is huge.
But it gets better: if you really find a performance bottleneck due to the use of immutability, you can fallback to mutability / place-oriented-programming.
Anyone who has spend a few days with Clojure realize how much more easier it is to reason about them and to work with them.
Immutable data structures combined the software transactional memory that Clojure provides are a godsend.
In a lot of case they're also much faster then the good old copy-on-write and because they're immutable you have lockless concurrency. This is huge.
But it gets better: if you really find a performance bottleneck due to the use of immutability, you can fallback to mutability / place-oriented-programming.