Ember Simple Form + Select2 value binding (untested)

gistfile1.js

Ember.EasyForm.Select.reopen({
  didInsertElement: function() {
    // Listen for select2 value changes.
    // Uses embers helper method to make sure this is bound correctly.
    // See: http://balinterdi.com/2014/05/09/ember-dot-run-dot-bind.html
    this.$().select2().on("change", Ember.run.bind(this, this.select2ValueChanged));
  },
...
  // When select2s value changes, update the components value
  select2ValueChanged: function(e) {
    this.set('value', e.val);
  },
  // When the components value changes, update select2s value
  valueChanged: function(value) {
    this.$().select2("val", value);
  }.observes('value'),
...
  willDestroyElement: function() {
    // Unbind select2 change listener
    this.$().select2().off("change");
  }
});