Ok, is there really a war between them? My opinion is they are currently covering different needs. Rails is a full-stack framework, very mature, used for fast prototyping and full-featured apps. Node.js is more focused on the fast and realtime web. I don't think anybody can get the productivity boost that you can get using rails with any other framework out there. But if you want a really fast and simple API logic, supporting websockets and have some nice specific libraries out-of-the-box, then node.js is a great solution (nginx with lua is also a great solution for websockets btw).
So, node.js is a low level solution, if your app is huge and have many features, then you better go with rails. Otherwise, choose node.js. Or combine them and use the best for each solution you need. There is a trend on one-page web apps which are focused to solve only one specific problem or for simple mobile APIs. I think that's the main reason that node.js is gaining so much traction... and the illusion that you are good to go learning only one language, "javascript" for back and frontend. So node.js is great to learn it and see where it can fit in your needs for boosting up some specific services.
So simple.
Oh and btw, regarding the speed of node.js, just check benchmarks with eventmachine (ruby) or twisted (python) vs node.js. Node.js isn't only about speed, is also about the supporting libraries they have around it for the specific problem that it tries to solve.