New Twiddle

application.controller.js

import Ember from 'ember';

const { Controller, on, get } = Ember;

export default Controller.extend({
	data: [],
	start: on('init', function() {
		const data = get(this, "data");

		for (let x=0;x<1000;x++)
		{
			const obj = {id:x,label:"o".repeat(10) + "_" + x,vis:false};

			data.pushObject(obj);
		}
		//Ember.run.later(this,this.make_visible,0,5000);	
	})
});

application.route.js

import Ember from 'ember';

const {
  Route,
  set
} = Ember;

export default Route.extend({

});

application.template.hbs

	{{data-item data=data}} 

data-item.component.js

import Ember from 'ember';

const {
  Component,
  computed,
  get,
  on,
  run
} = Ember;

export default Component.extend({

	itemComponent: computed('item.vis', {
    get() {
      return get(this, 'item.vis') ? "item-visible" : "item-hidden";
    }
  }),
  
  start: on('didInsertElement', function() {
    run.later(this,this.make_visible,0,5000);	
  }),
  

	make_visible(idx)
	{
		const data = get(this, "data");

		Ember.set(data[idx++],"vis",true);

		if (idx < data.length)
		{
			Ember.run.later(this,this.make_visible,idx,50);
		}
	}
});

data-item.template.hbs

{{#each data as |item|}}
  {{#if item.vis}}
   {{item-visible}}
  {{else}}
   {{item-hidden}}
  {{/if}}
{{/each}}

item-hidden.template.hbs

hidden

item-visible.template.hbs

visible

twiddle.json

{
  "version": "0.4.13",
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/1.13.10/ember.debug.js",
    "ember-data": "https://cdnjs.cloudflare.com/ajax/libs/ember-data.js/1.13.13/ember-data.js",
    "ember-template-compiler": "https://cdnjs.cloudflare.com/ajax/libs/ember.js/1.13.10/ember-template-compiler.js"
  }
}