I love that everything custom must go into wp-content. I love that any custom theme functions are supposed to go in functions.php. This keeps things easy to isolate and debug. Its an extreme whose opposite is Drupal, where some obscure functionality can be popping off in one of hundreds of .module or .tpl files.

Its pretty much summed up by "my gag reflex kicks in at the mention of a Drupal contract, WordPress is still pleasant-ish to work with".