If I am to build a real-time MMO, multi-room based, non-persistent world, which offers the best vertical scalability [consider mainly the number of players served on same machine, and ram footprint]?
Are Socketstream and Now.js ready to use new Node.js 0.6 Cluster module?
You will have to custom code a solution using the v0.6.x clustering. It came out very recently and besides being very basic, has not had time to be baked into any libraries yet.
I would suggest you look at http://learnboost.github.com/cluster/
It won’t work with v0.6.x as far as I’m aware, but according to this issue https://github.com/LearnBoost/cluster/issues/168
Tj is “on it”.