As the name implies, Engine Yard's Labs provides experimental features for users so that the company can get quick feedback from customers. The emphasis is on experimental, though, because there's no promise that support will make its way out to production.
According to Dr. Nic Williams post, "features released through Engine Yard Labs are not officially supported and may or may not become supported as a part of Engine Yard products in the future."
To get access, developers sign up on the early access page and request to have the feature enabled.
Note that pre-supported software is not new to Engine Yards. The company has had alpha and beta features for some time. MySQL 5.1 and 5.5 as well as PostgreSQL 9 are in alpha right now, along with MongoDB and Rubinus. GitHub account linking is currently in beta.
What do you think? Is there enough demand for Node.js for Engine Yard to promote it to the supported platforms? Is it a good idea for PaaS providers to experiment with features they may not roll out at all?