You have the ability to view your friends on a map from the Places area, the ability to unfriend someone, an improved News Feed and notifications UI.
But the big thing is the Facebook Event check-ins. Previously, you could only check-in via Facebook Places. That meant checking-in to various locations around cities just like you do on Foursquare, Gowalla, Loopt, and others. But now that you can check-in to events themselves, it opens a range of possibilities. You could run contests at events through this, for example.
What's New in Version 3.4
- Added Map View for Places
- Added the ability to Check in to Events that you're attending
- Added the ability to unfriend from the phone
- Improved News Feed
- Improved notifications UI