How do you get the current user object in Joomla 1.5?

In Joomla 1.0, the current User object was stored in a global variable called $my. This doesn't exist in Joomla 1.5 any more - how do I get that object? Also, how can you tell if the user hasn't logged in?

From stackoverflow

• Information found at http://docs.joomla.org/Accessing_the_current_user_object

  $user =& JFactory::getUser();
  

  And how to tell if they've logged in, or if they're just a guest:

  if ($user->guest) {
      echo "Please log in.";
  } else {
      echo "Welcome!";
  }