It turns out the Windows 7 M3 build 6801 has a hidden early version of the new taskbar that was demonstrated in the PDC keynote. Rafael over at WithinWindows has figured out a clever way to enable the new taskbar. By default, the new taskbar is hidden when the machine is not joined to a Microsoft domain. Rafael has released a program that bypasses that protection and allows the new taskbar to start up.
The version included in build 6801 is not feature complete and has a number of issues which is probably why it was hidden in the M3 build. When enabled the classic quick launch bar is still visiable but that can be easily hidden by right clicking on the taskbar, going to Toolbars and unchecking Quick launch.
Read more at Within Windows