Standard Node.js, Javascript, and npm vitrol aside, I think this post covers an interesting topic of balancing progress with stability. I'm sure everyone has their own opinion on what is too fast (breaking things) or too slow (lacking modern language features and engine improvements), but the model they describe seems to do a pretty good job of appeasing both agile and inertial clients.
Still, a rapid release cycle for the engine could wreak (and to some extent has wreaked) havoc with the npm module ecosystem not keeping up.