Last evening the new Facebook iPhone application went live in the iTunes application directory. The new features are push notifications and contact sync. There are a number of notifications that you can receive, though you’ll probably want to customize them as to avoid getting overwhelmed with constant updates.
Currently notifications can be controlled for messages, wall posts, friend requests, friend confirmations, photo tags, events, and comments. If you are an extremely active Facebook user, modifying these settings is something you'll want to do. You can modify them by going to “Settings” on the iPhone and scrolling down to the Facebook application. The contact sync feature is also very useful as it lets you instantly add the photos of friends on to your phone.
Go here to download the new App on iTunes.