Developer Preview, not a mere pre-beta release, pre-alpha more likely
It was meant to show direction that Microsoft is headed with development. The main point being Metro styled apps need to be developed by developers. They did not include all the functionality of the start screen, which after reading the blog is quite a bit. The start screen is kind of a merger of the Start Menu, the taskbar, and the desktop. Once they iron out the transition of clicking on the start button, and increase the size of icons for desktop programs, it will make sense.