exactly what rails has become to me. Models and API controllers that respond_to json. The client does the rest with Backbone, handlebars, css3 animations, ...
While I like what Meteor is attempting to do by merging the client and server into one framework, I feel their approach is somewhat haphazard. Using it left a bad taste in my mouth, though t be fair I haven't done much beyond building a basic app for evaluation purposes. I'm currently evaluating Derby.js, and so far I'm liking it much more.
That said, convention has yet to be established for clientside apps, so either framework could fail. I do think that there is a niche for a framework that provides both the server and the client, however.