This one is a little bit more esoteric. I found the need change the page style (via CSS) based on whether the current user had permission to update the current node. Drupal preprocess_page to the rescue!
Just add this snippet to the yourTheme_preprocess_page function in your template.php file. It will add body classes (e.g., user-node-update, user-node-delete) to your page depending on the current user's permission to access the node being viewed.