I should have been more descriptive than "will not work" sorry. As you said, it does launch but it launches behind the Metro screen, it does not get rid of the Metro screen on boot the way launching "explorer.exe" does. Also, once you click to the desktop from Metro, even if you had ehshell.exe open behind it in fullscreen mode, it is still behind the taskbar.
If you had another task that switched to the desktop and then launched ehshell.exe, that might work but I haven't tried it.
I'm pretty sure I know a way to programmatically do it but I'm still in the process of building my Win8 development machine so I haven't tested it yet.