Whilst UDP is all well and good. ..Is there perhaps some confusion between that and well designed architecture.
I believe good multi-player gaming can be achieved with TCP.
First off all, we need a optimised methods of transit and a means - socket.io. Many guys here have already demo'd the use of this.
We should, in theory (and with some mods), be able to use c2runtime.js on both server and client side with some 'middleware' that deals with Client Side Prediction and Entity Interpolation.
What's interesting about the above article is the structure of the game:
client.js - The logic for the game client setup in the browser.
app.js - The server side app to run on node. This handles all the node/express/socket.io set up and code.
game.server.js - The logic for the game server (?lobby?).
game.core.js - The logic for the game play itself, both server and client.
Until I've created for myself and failed or seen a game output here with these methodologies, I can't believe it can't be done (double negative ;))