In one of our Drupal production site, we have around 84K nodes. Periodically we need to rebuild the content access permission, which takes around 6 hours to complete when done through the browser. Being very unhappy with it, today found the following drush use:

Emrans-MacBook-Air ~: drush php-eval 'node_access_rebuild();'

The results were immediate, the whole rebuild now takes only 20 minutes!