We have a lot of chosen in our ember app, and extracted this superclass to make interaction with them easier, it takes care of refreshing/filling/selecting stuff.

// fix chosen picks up ember script tags -> weird output when search for t or i
// this breaks the bindings within the options tags
// works around https://github.com/harvesthq/chosen/issues/581
App.UnboundSelectOption = Ember.SelectOption.extend({
  template: Ember.Handlebars.compile('{{unbound label}}')
});

App.ChosenSelect = Ember.Select.extend({
  chosenOptions: {},

  template: Ember.Handlebars.compile(
    '{{#if prompt}}{{unbound prompt}}{{/if}}' +
    '{{#each content}}{{view App.UnboundSelectOption contentBinding="this"}}{{/each}}'
  ),

  didInsertElement: function(){
    this._super();
    this.$().chosen(this.chosenOptions());
  },

  _closeChosen: function(){
    // trigger escape to close chosen
    this.$().next('.chzn-container-active').find('input').trigger({type:'keyup', which:27});
  },

  rerender: function(){
    if(this.get('state') == 'inDOM'){
     // remove now disconnected html
      this.$().next('.chzn-container').remove();
    }
    this._super();
  },

  rerenderChosen: function() {
    this.$().trigger('liszt:updated');
  }
});

We had a lot of pain sorting our collections, since they are not there when the page is opened you need to continually re-sort…

App.Controller.Events = Ember.ArrayController.extend({
    init: function() {
      this._super();
      Helper.assignSortedCollection(this, 'content', Oceans.store.findAll(Oceans.Model.Event), function(item){
        return -1 * item.get('created_at').getTime();
      });
    }
  });

Helper = {
  assignSortedCollection: function(to, path, items, sorter){
    items.addObserver('length', function(){
      var temp = Ember.A();
      this.forEach(function(item) { temp.pushObject(item); });
      to.set(path, _(temp).sortBy(sorter));
    });
  }
}

You want to do something when your record got saved/validations failed.

Usage

user.observeSaveOnce(success: function(){
  // go to next page
}, error: function(){
  // show validation errors
})

Code

  # your model.js 
  observeSaveOnce: function(options) {
    function callback() {
      var outcome = 'success';
      if (this.get('isDirty')) {
        if (this.get('isValid')) return; // not submitted yet
        outcome = 'error';
      }

      (options[outcome] || Ember.K).call(this);

      this.removeObserver('isDirty', callback);
      this.removeObserver('isValid', callback);
    }

    this.addObserver('isDirty', callback);
    this.addObserver('isValid', callback);
  }