I'm not very familiar with Node, but I had assumed that a more flexible or movable client/server dividing line was the point of Node, and assumed it's what people were already doing... but maybe not. Can any Node afficianados speak to this question?
I am not an afficianado by any means, but it does help in some ways. Many libraries exist that can run on both sides of the connection. Unfortunately, I haven't found much that allow you to modify the DOM/html using the same code on client and server, and even less that allows you to go from an application state on the server into an identical state on the client. Meteor.js, Opa, and Derby.js seem to be the main options in this field, but I'd like to see a simple javascript library that facilitates this so that many other frameworks can take advantage of it.