woothemes/woocommerce — pull request #1488 by neilpie (2012-09-09 14:29:38+00:00)
Title: Added 'woocommerce_order_status_changed' hook

Something that I've found would be useful is the ability to access the before and after statuses when an order status is changed. I can't see another way of accessing this information without hooking onto 'woocommerce_order_status_' . $this->status . '_to_' . $new_status->slug with all possible permeatations.

Unless I'm missing it somewhere and you can point me in the right direction?