Basing this on the screencast I think this looks amazing and they seem to be very productive. This said, I am unsure if this would produce codebases that are easier to maintain, since there is not a clear separation of concerns and everything seems to be connected. I think doing client-side JavaScript is hard and messy (even with Backbone or Ember) I could not imagine this would be any easier if I had to handle the backend on the client-side as well (especially a backend that's updated in realtime).

This said, maybe the current struggle of the client side is because the data is on the backend and needs to be fetched, updated and handled using a client-server model. With Meteror the data seems to live on the client-side which maybe makes things easier.