CakePHP Questions

For a long time I used this method of passing variable to view:

public function index(){
    $this->set('items', $this->paginate());
    $this->set('promos', $this->Promo->getRandomPromos(5));
}

OR

public function index(){
    $items = $this->paginate());
    $promos = $this->Promo->getRandomPromos(5);
    $this->set(compact('items', 'promos'));
}

recently I found that $this->data array of controller is passed to view, so basicly I achive similar effect with this

public function index(){
    $this->data['Items'] = $this->paginate();
    $this->data['Promos'] = $this->Promo->getRandomPromos(5);
}

In view though, you can not access it as local var, so you have to use $this->data to access value.

Basicly my questions is how you do that, and is there is any catches of using $this->data as container for passing vars?