It's difficult to overstate the importance of the principles taught in this talk. Almost as difficult as it is to describe why they are so important. The fundamentals of quality software are found here, not in some Martin Fowler dissertation on DDD.
I think the general concept of using immutability, queues, and isolating side effects, is lost and muddied by using Ruby, and it's a misuse of the term "functional."
Edit: correction from commenter, thanks!