I have this working ember snip: http://jsfiddle.net/wUC9w/
with the following 2 models:
App.Card = DS.Model.extend
  title: DS.attr("string")
  description: DS.attr("string")
  template: DS.belongsTo("template", {async: true})
App.Template = DS.Model.extend
  title: DS.attr("string")
  cards: DS.hasMany("card", {async: true})
However it's refusing to connect the two models in the cards view, (it doesn't get the title of the linked template). I've tried using {async: true} side-loading and preloading the related template model in the app but ember still doesn't connect the two.
I've looked all over the ember docs and asked in IRC with much help but no luck, Any observations would be greatly appreciated!