The only problem with this approach is it doesn't support booting on different computers well.
Windows 8 To Go (Enterprise version only though) is a lot better in this respect. It installs drivers on the first boot to a new machine, and then uses the setup on subsequent boots. I tried it to switch between a Radeon and an Nvidia machines, works like a charm. Also win8 doesn't need a frankenbuild, install to an external disk is supported out of the box.