Hope you don't mind the flamboyant title, but, I truly do believe that the small attack surface of the heavily minified Xen hypervisor, networking stack, GUI virtualization, and much more Qubes OS employs + the Whonix intergration implemented in this project (making it a Windows-Whonix-Workstation; thus also giving it Tor-only Internet access with stream isolation between other VMs) makes it the most secure and private way to use Windows currently available today. Those are just the two main points, besides that, there is also the fact that because everyone using this project is both having their Windows VMs set up in the same way and running Qubes OS, that greatly helps to keep the OS and hypervisor fingerprint homogeneous across all users. This effect will only grow stronger as the Qubes OS userbase increases. Lastly, if the user wishes to reset their fingerprint, they can automatically do so by reinstalling Windows with this project.
Of course, I would be happy to go into detail and answer questions about any of this.
Note that this project is the product of an independent effort which is not officially endorsed by Qubes OS or Whonix.