title: Is there an issue in ember RC6?
body: <p>I updated to RC6 two weeks ago, and I'm noticing an error in one of the screens in the project I'm working on. I have an ember model, which has a hasMany relation, that model as a computed property based on a property on its hasMany relationship, something like this:</p>
  
  <pre><code>notReadyToSend: function() {
    return this.get('tweets').filter(function(tweet){
      return !tweet.get('readyToSend');
    })
  }.property('tweets.@each.readyToSend')
  </code></pre>
  
  <p>this belongs to the tweet model:</p>
  
  <pre><code>readyToSend: function() {
    //if all properties are true, then this property returns true 
  }.property('title', 'body', 'alreadySent', and many other properties)
  </code></pre>
  
  <p>and, at the time in which the data is being loaded, all the tweets are not 'ready' because you know, data is being loaded, but when the whole data is loaded, some tweets remain not 'ready' in the 'notReady' property, but they are actually 'ready' in their object, I mean, the Tweet ember model hast its 'ready' property, which also has some logic, and that property is true, but the 'notReady' property is not fired, and this happens for the last(depends how many we have, sometimes only one, sometimes two, etc) tweets.</p>
  
  <p>Is anyone experiencing this issue ?</p>
  
  <p>I've updated the code, but as a note, those are not the real models, but that's basically what I'm doing. the readyToSend property, gets set to true for all records, but the notReadyToSend property in the parent model, doesn't get updated, but again, this does not happen with all the records, just a few ones(and only the last in in the relationship) do not fire the parent property.</p>
  
  <hr>
  
  <p>One more update, I have another property in the parent model, which also checks one property of the tweets relationship, it looks like this:</p>
  
  <pre><code>hasAtLeastOneTweetALreadySent: function() {
    return this.get('tweets').findProperty('alreadySent');
  }.property('tweets.@each.alreadySent')
  </code></pre>
  
  <p>and the 'alreadySent' property is also being observed in the 'readyToSend' property of the tweet model. And for some reason, if I just comment out that(hasAtLeastOneTweetALreadySent) property, everything works fine, do you know why this is happening ? this is weird.</p>