With Windows 8.1 Microsoft finally recognizes that a big portion of the world actively dislikes the new "Modern" interface and Start screen, and lets people downplay it, bypass it, or make it work the way they like. It doesn't solve the basic problem of Windows 8 having dueling interfaces -- one for touch and tablets, and another for the desktop and mouse and keyboard -- but it gives desktop fans enough options to make the operating system much better to use.
Big changes include the ability to go directly to the desktop when you sign in, and a whole host of Start screen customizations that make it more useful for those who primarily use the desktop. There's also now a not-particularly useful Start button that doesn't come close to having the features offered by the old school Start button you've come to love in earlier Windows versions.
If you're like me, what you care about most about is the go-to-desktop option, and changes that make the Start screen easier to use. You would expect that you'd get to those changes from the Start screen somewhere...but if you expected that, you'd be wrong. Instead, head to the desktop, right-click the taskbar and select Properties to get to the Taskbar and Navigation properties screen. There's a new tab here called Navigation. This is essentially command central for the new features for customizing the Start screen and booting to the desktop. It's got two sections: Core navigation and Start screen.