Facebook app for Windows Phone has been updated to version 2.2. With the update, it brings you fast switching (for WP7.5) and also Toast and Tiles notifications.
One of the major highlights is that you can also pin messages, new feed and etc to the home screen. For those who have not had any update notification, you can actually go to Windows Phone site and reinstall the software.
I tried the app. Fast switching works and pin to start function is also there. Always nice to get such update.