The preview of Windows 8.1 is now available for download at, http://windows.microsoft.com/en-us/windows-8/preview.
I installed it earlier today and I got a start button that I never will use. But is good that they added it when it seems to be an important thing for a lot of people.
I like that I can use a photo as background at the startscreen and that it is easier to adminstrate the tiles on the start screen. For users with touch screen it's good that you can do all settings from the PC-settings app and don't need to use the control panel.