"Meteor 0.5.0, available today, allows you to write secure realtime client-server applications in pure JavaScript. It's the only system of its kind in the world." That's an outright lie. cf. http://opalang.org
SocketStream http://socketstream.com lacks the media blitz, but it provides authentication and integrates with pretty much anything in NPM (one of the stated goals of the author), and still provides all the benefits of a real-time framework like Meteor (for more than a year now)
It doesn't do much yet, but shows the direction I'm going in: More API based, pipeable Node Streams wherever possible, full npm / Node compatibility. Follow @socketstream for updates.
Also I want to congratulate the Meteor team on their release. Making scalable, reliable realtime web apps is hard and all work in this area benefits the entire community.