This update brings into the main app features that were previously only available in beta, such as the ability to upload videos taken on the phone directly from the app. The app also supports more languages, as well as integration with Facebook Messenger.
Windows blogged about the updated app:
Today, Facebook for Windows Phone is receiving a major update that brings an updated design and new features that were previously available in beta. Along with the overhauled user experience and improved app performance, Facebook for Windows Phone now supports more languages and has the ability for you to upload videos taken with your Windows Phone device directly to from the app. It also supports integration with Facebook Messenger for Windows Phone. And for devices with Windows Phone 8.1, it will now connect directly with the People Hub. In Windows Phone 8.1, Facebook contacts, events, and photo albums are now powered by the Facebook for Windows Phone app. If you have the app, you should receive the update shortly. If you don’t have it, download it here from the Windows Phone Store.