Library vs. Controller

[eluser]dmiden[/eluser]
Basically I use the libraries for classes that are used on all sites,
f.ex. I have a User library which handles login/logout/userdata etc.
This library has public $vars that are assigned when the class initialized.
So in my controllers I can f.ex. do this

Code:

function index()
{
   if ($this->user->authed == FALSE)
   {
      redirect('login/');
   }
}

The models are used for actions that arent used on all controllers.
F.ex. admin_model which handles all administration.