I think he's missing the point by focusing on the GUI -- it's a uniform
userland, not a uniform appearance, that facilitates interoperability. User
management, permissions and a model for resources go a long way toward
making a platform.
As Firefox, Silverlight & al. become more and more like desktops,
virtualization allows Linux to become more like a cross-platform application
environment. Web apps often find themselves recreating userland fundamentals.
The people at Vita Nuova caught on to this a few years ago, and released a
version of Inferno (Unix relative) as a browser plugin.