usernames.js

template = template.replace(/@(\w+)/, "{{view Scvrush.UserLinkView username='$1'}}");
usernames = template.match(/@(\w+)/);

controllerFor('controllerWithText').set('usernames', usernames);

Scvrush.ControllerWithText = Em.Controller.extend({
init: function() {
  var usernames = this.get('usernames'),
      loadedusers = Scvrush.User.all();

  usernames = usernames.filter(function(username) {
    return !loadedusers.findProperty('username', username);
  });

  loadingusers = Scvrush.User.findQuery(usernames: usernames);
  
  this.set('loadedUsers', loadedusers);
  this.set('loadingUsers', loadingusers);
}
});

view.js

Scvrush.UserLinkView = Ember.View.extend({
  tagName: "span",
  
  didLoadUsers: function() {
    if (this.get('controller.loadingUsers.isLoaded') {
      this.notifyPropertyChange('user');
    }
  }.observes('controller.loadingUsers.isLoaded'),
 
  user: function() {
    return this.get("controller.loadedUsers").findProperty('username', this.get('username'));
  }.property('username'),
 
  template: Ember.Handlebars.compile("{{#if view.user}}{{#linkTo 'user' view.user}}@{{view.user.username}}{{/linkTo}}{{else}}@{{view.username}}{{/if}}")
});