If you already own a copy of Windows 8, this is the day you may have been waiting for. Effective immediately, Microsoft's Windows 8.1 update is available to download and install for free, provided you already own a copy of Windows 8 (you should see a notification in the Windows Store). If not, you can pre-order the full version of Windows 8.1 for $120 from the Microsoft Store, which will begin shipping out tomorrow.
Installing the update over the top of Windows 8 is supposed to be an easy process. We recommend doing a full backup beforehand, especially if you're toying with a mission critical system, but in theory the update shouldn't muck with your programs, saved files, or settings.
Windows 8.1 is a major update to Microsoft's touch oriented OS. It includes a new version of Internet Explorer that's better optimized for touch and has split-screen browsing capabilities, an enhanced Windows Store, different size Tile options, the return of the Start button (takes you to the Start screen if you're in Desktop mode), and more.