Perhaps you can clear up my confusion with the article. It appears to me that Play is basically implementing Rx, except with a pointless new set of terminology. The Node examples could have all been structured almost identically to the Play examples if they used rx. What advantages or extra functionality is enabled by enumerator/enumeratee/iteratee that you can't get with observable?
Play didn't invent the iteratee concept, Oleg Kiselyov did (http://okmij.org/ftp/Streams.html). I asked myself the same question, as I'm doing the reactive programming course on Coursera, where Rx was the topic of the last couple weeks. I came to the conclusion that Rx focuses on side-effects while iteratees concentrate on iterative calculations. Iteratees calculate a result while Rx-observers just perform side-effects.
Maybe someone else can further elaborate on this topic.
Quoting Roper: The complexity of iteratees comes because they handle many different things at once - async io, backpressure, producing results, composition on multiple different axes. Most other APIs that they get compared to only handle one or max two of these, so the complexity of those APIs is not in what they do, but what they don't do that you have to implement yourself.
