The App Store description still contains information for version 2.5; however, the actual download is now version 3.0. I simply deleted my previous Facebook app from Applications then redownloaded it to update to the new version.
So Whats New in This Update?
1. The "new" News Feed
3. Events (including the ability to RSVP)
6. Create new photo albums
7. Upload photos to any album
8. Zoom into photos
9. Easier photo tagging
10. Profile Pictures albums
11. A new home screen for easy access to all your stuff, search, and notifications
12. Add your favorite profiles and pages to the home screen
13. Better Notifications (they link to the comments so you can reply)
14. Quickly call or text people right from the Friends page
15. Messages you are typing will be restored if you quit or are interrupted by a phone call
16. Video uploads for the 3GS