I love it! As rails matures and is used on bigger and bigger projects, it starts to look more and more like Java. It used to be all about rapid development... but now we're all talking about performance, and threads, and service layers. Thank god node.js is here to remind us that we really don't need any of that crap.
Jared suggests using services to translate into different protocols. I see a further use for services to translate models into different representations on the same protocol in order to support a versions API. Let a service handle mapping outdated API payloads to the latest version of the domain model.