This feels to me a lot like how Rails felt back in 2005. A fundamental leap forward and an understanding of where web technology is going. I haven't felt that way about Node.js or even its higher-level frameworks like Express or Batman. This feels like "The One", even though I've been absorbing the docs and screencasts only for the last 20 minutes.
This is built with Node.js. From the docs: "A Meteor application is a mix of JavaScript that runs inside a client web browser, JavaScript that runs on the Meteor server inside a Node.js container..."
Node.js is very low level and is more analogous to Ruby than Rails.