This question goes out to anyone that's used or tried to use node.js in a serious project. How stable is it? What did you use it for? How robust is it?
Personally, I haven't used it in production but I know several companies already did. For example, GitHub uses Node.js to power the download server.
The bottom of the index page of the node.js wiki on github lists a number of companies that are using node.js, some apparently for live and public applications which would generally be considered to be "in production".