Co-routines are great! Have been using them as part of Common Node (https://github.com/olegp/common-node) via node-fibers for a number of projects. Both stability and performance have been admirable.
For example at StartHQ (https://starthq.com) we have a framework that automatically fetches data about web apps from a number of sources, some as frequently as once every few minutes (blog RSS feeds) for all the 2K+ apps. At the same time we've had as many as a few hundred concurrent visitors on site at peak, all on an EC2 micro instance, with no noticeable impact on responsiveness.
For example at StartHQ (https://starthq.com) we have a framework that automatically fetches data about web apps from a number of sources, some as frequently as once every few minutes (blog RSS feeds) for all the 2K+ apps. At the same time we've had as many as a few hundred concurrent visitors on site at peak, all on an EC2 micro instance, with no noticeable impact on responsiveness.