I've recently moved from using Gmail to Hotmail.
When I use Gmail on my Windows Phone, I'm able to see that the labels are used as folders in the mail client on the phone. This really helps me sort my mail.
However, the Hotmail categories I've set up on the main website do not seem to translate from the web to WP7, nor to the Mail app in Metro.
Will this be implemented in the final release of Windows 8? It would really help to sort and categorise mail if the Hotmail features could be used in the same way in Metro, too.