[pmarreck]

In my case I found I was already starting to write Ruby in a very functional way (PORO which is like POJO, only setting properties at object instantiation, focusing on data expressed in built-in classes instead of custom classes, etc.) and that seemed to ease the transition quite a bit.

I've found that "immutability all the way down" has eliminated an entire class of bugs related to unexpected mutation, deadlocking/concurrency issues, etc.