I have now spend two weeks of sleepless nights exploring node.js. I installed it on my mac, the actually created an Amazon EC2 Ubuntu box, so that I can sandbox my test sites. While I am going through a lot of learning pain and now starting to love the approach, the paradox is that as a JavaScript geek, I am having a hard time to find a use case for building something in node.js. The direction I am going is really more all business logic to the browser, so all I really need the server to do is to be the middleware: good solid DB and easy fast scalable way to access it, and for this purpose node.js seems to be way to immature at this point. I cannot imagine migrating my large SQL Server relation databases on which some of my social networking sites or business apps run to mongoDB, and being able to do all the backups, and scaling that come with it.
The one feature I do like is the event based server, which is great for realtime apps like chat, or stock streaming, so this might be something that node.js will get get shot...