The official launch of Windows 8.1 is here. Back in mid-August the launch for Windows 8.1 was officially confirmed to happen on October 17 in the US. October 17 is today if you aren't keeping track. If you're planning on installing Windows 8.1 straightaway and happen be a heavy Facebook user, you will be glad to hear that an official Facebook Windows 8.1 app has turned up as well.
Reports indicate that users who have the RTM version of the Windows 8.1 update have been able to download the Facebook Windows 8.1 app directly from the Windows Store. That means later today once you get the Windows 8.1 update installed on your computer, you'll be able to logon and download the app right away.
The official Facebook app is designed to use the Modern UI. The availability of the Facebook app for Windows 8.1 users confirms a previous rumor that the app would be launching alongside the Windows 8.1 update.
You can certainly expect basic Facebook functionality, but any specific features the Windows 8.1 app offers are pretty much unknown. One thing we do know is that any updates from Facebook will appear on the Windows 8.1 Start screen. That may well be the only difference in Windows 8.1 version of the app compared to other Facebook clients.