hook_user problem / perhaps bug in 4.7-beta3

Hi

I didn't really want to post to the core forum but I am 99% sure that Drupal isn't doing what its supposed to. I modified block_example by
removing all the comments and adding a call to _user. I tried to add something to $user so I can use it later. The wording in the API leads me to believe this is possible. I try to display the thing I add in the block but it doesn't show up. All the code is here:

<?php
function block_example_help($section) {
  switch ($section) {
    case 'admin/modules#description':
      // This description is shown in the listing at admin/modules.
      return t('An example module showing how to define a block.');
  }
}

function block_example_block($op = 'list', $delta = 0, $edit = array()) {
  switch ($op) {
    case 'list':
      $blocks[0]['info'] = t('Example: configurable text string');
      $blocks[1]['info'] = t('Example: empty block');
      return $blocks;
    case 'configure':
      $form = array();
      if ($delta == 0) {
        $form['block_example_string'] = array(
          '#type' => 'textfield',
          '#title' => t('Block contents'),
          '#size' => 60,
          '#description' => t('This string will appear in the example block.'),
          '#default_value' =>
            variable_get('block_example_string',  t('Some example content.')),
        );
      }
      return $form;
    case 'save':
      if ($delta == 0) {
        variable_set('block_example_string', $edit['block_example_string']);
      }
      return;
    case 'view': default:
      switch ($delta) {
        case 0:
          $block['subject'] = t('Title of block #1');
          $block['content'] = block_example_contents(1);
          break;
        case 1:
          $block['subject'] = t('Title of block #2');
          $block['content'] = block_example_contents(2);
          break;
      }
      return $block;
  }
}
function block_example_contents($which_block) {
global $user;
  if ($which_block == 1) {
    $output = variable_get('block_example_string',  t('A default value.'));
    $output .="<br />user name is : $user->name";
    $output .="<br />user special string is : $user->specialstring";
    return $output;
  }

  if ($which_block == 2) {
    return;
  }
}

function block_example_user($op, &$edit, &$user, $category = NULL) {
  switch ($op) {
    case 'load':
        $user->specialstring = "Hello World";
    break;
  }
}
?>

Is this a bug or a misunderstanding on my part?

Any advice or pointers would be greatly appreciated!

Thanks,

Mark