Drupal - Views and node count for taxonomy terms

1. Create a taxonomy view
2. Add node group in relationship
3. Add term name and node nid fields for display
4. Enable aggregation in "Other" section (Use aggregation: Yes)
5. Click nid field settings icon, choose group type "count".

Find the export of views that worked for me.

$view = new view;
$view->name = 'term_node_count';
$view->description = 'Displays node count values for terms';
$view->tag = '';
$view->base_table = 'taxonomy_term_data';
$view->human_name = 'term_node_count';
$view->core = 7;
$view->api_version = '3.0-alpha1';
$view->disabled = FALSE; /* Edit this to true to make a default view disabled initially */

/* Display: Defaults */
$handler = $view->new_display('default', 'Defaults', 'default');
$handler->display->display_options['use_ajax'] = TRUE;
$handler->display->display_options['group_by'] = TRUE;
$handler->display->display_options['access']['type'] = 'none';
$handler->display->display_options['cache']['type'] = 'none';
$handler->display->display_options['query']['type'] = 'views_query';
$handler->display->display_options['exposed_form']['type'] = 'basic';
$handler->display->display_options['pager']['type'] = 'full';
$handler->display->display_options['pager']['options']['items_per_page'] = '100';
$handler->display->display_options['pager']['options']['offset'] = '0';
$handler->display->display_options['pager']['options']['id'] = '0';
$handler->display->display_options['pager']['options']['expose']['items_per_page_options_all'] = 0;
$handler->display->display_options['style_plugin'] = 'table';
$handler->display->display_options['style_options']['columns'] = array(
  'name' => 'name',
  'nid' => 'nid',
);
$handler->display->display_options['style_options']['default'] = '-1';
$handler->display->display_options['style_options']['info'] = array(
  'name' => array(
    'sortable' => 0,
    'default_sort_order' => 'asc',
    'align' => '',
    'separator' => '',
  ),
  'nid' => array(
    'sortable' => 0,
    'default_sort_order' => 'asc',
    'align' => '',
    'separator' => '',
  ),
);
$handler->display->display_options['style_options']['override'] = 1;
$handler->display->display_options['style_options']['sticky'] = 0;
/* Relationship: Taxonomy: Node */
$handler->display->display_options['relationships']['nid']['id'] = 'nid';
$handler->display->display_options['relationships']['nid']['table'] = 'taxonomy_index';
$handler->display->display_options['relationships']['nid']['field'] = 'nid';
$handler->display->display_options['relationships']['nid']['required'] = 0;
/* Field: Taxonomy: Term */
$handler->display->display_options['fields']['name']['id'] = 'name';
$handler->display->display_options['fields']['name']['table'] = 'taxonomy_term_data';
$handler->display->display_options['fields']['name']['field'] = 'name';
$handler->display->display_options['fields']['name']['alter']['alter_text'] = 0;
$handler->display->display_options['fields']['name']['alter']['make_link'] = 0;
$handler->display->display_options['fields']['name']['alter']['absolute'] = 0;
$handler->display->display_options['fields']['name']['alter']['trim'] = 0;
$handler->display->display_options['fields']['name']['alter']['word_boundary'] = 1;
$handler->display->display_options['fields']['name']['alter']['ellipsis'] = 1;
$handler->display->display_options['fields']['name']['alter']['strip_tags'] = 0;
$handler->display->display_options['fields']['name']['alter']['html'] = 0;
$handler->display->display_options['fields']['name']['element_label_colon'] = 1;
$handler->display->display_options['fields']['name']['element_default_classes'] = 1;
$handler->display->display_options['fields']['name']['hide_empty'] = 0;
$handler->display->display_options['fields']['name']['empty_zero'] = 0;
$handler->display->display_options['fields']['name']['link_to_taxonomy'] = 1;
/* Field: Node: Nid */
$handler->display->display_options['fields']['nid']['id'] = 'nid';
$handler->display->display_options['fields']['nid']['table'] = 'node';
$handler->display->display_options['fields']['nid']['field'] = 'nid';
$handler->display->display_options['fields']['nid']['relationship'] = 'nid';
$handler->display->display_options['fields']['nid']['group_type'] = 'count';
$handler->display->display_options['fields']['nid']['label'] = 'Count';
$handler->display->display_options['fields']['nid']['alter']['alter_text'] = 0;
$handler->display->display_options['fields']['nid']['alter']['make_link'] = 0;
$handler->display->display_options['fields']['nid']['alter']['absolute'] = 0;
$handler->display->display_options['fields']['nid']['alter']['trim'] = 0;
$handler->display->display_options['fields']['nid']['alter']['word_boundary'] = 1;
$handler->display->display_options['fields']['nid']['alter']['ellipsis'] = 1;
$handler->display->display_options['fields']['nid']['alter']['strip_tags'] = 0;
$handler->display->display_options['fields']['nid']['alter']['html'] = 0;
$handler->display->display_options['fields']['nid']['element_label_colon'] = 1;
$handler->display->display_options['fields']['nid']['element_default_classes'] = 1;
$handler->display->display_options['fields']['nid']['hide_empty'] = 0;
$handler->display->display_options['fields']['nid']['empty_zero'] = 0;
$handler->display->display_options['fields']['nid']['link_to_node'] = 1;

/* Display: Block */
$handler = $view->new_display('block', 'Block', 'block_1');
$translatables['term_node_count'] = array(
  t('Defaults'),
  t('more'),
  t('Apply'),
  t('Reset'),
  t('Sort By'),
  t('Asc'),
  t('Desc'),
  t('Items per page'),
  t('- All -'),
  t('Offset'),
  t('node'),
  t('Term'),
  t('Count'),
  t('Block'),
);

All the previous answers were very helpful.

I wanted to get a table so I could let the user sort by Term or by count.

To do this I:

1. Relationship > Taxonomy term: Content with term
2. Use aggregation: Yes
3. Field > Content: Nid
4. Aggregation type for Nid = Count DISTINCT

To get a taxonomy node count correctly for taxonomy terms you need to do the following:

1. In Fileds: add Taxonomy term: Name
2. In Relationships, add a Taxonomy term: Content with term

3. Add a contextual filter for Taxonomy term: Name

   3a. Choose 'Display a summary'

   3b. Choose 'Display Record count with link'. Also set base path if you want the taxonomy page to be linked correctly.