Logging to the system log is useful for those times when you need to know what's happening during, say, a PayPal IPN transaction. I've done this by modifying workflow_ng_show_log()

function workflow_ng_show_log($log) {
  ...
    drupal_set_message(implode('<br />', $output));
    watchdog('workflow-ng',implode('<br />', $output),WATCHDOG_NOTICE);
  ...
}

I'd like to see something to toggle this behavior, even perhaps a UI.

Don