Metro UI can be turned off, reverting to what is basically a Win7 UI unless you open a Metro app. Metro apps always run in the Metro UI. At least that's my understanding.

Of course they want testing and feedback on Metro, because as you say, the real point of Win8 vs Win7 is unification of developement and the introduction of a unified app store for desktop, tablet and phone Win versions.

That said, and to get back on-topic, I don't see any comparable effort on the Linux side to integrate and unifiy desktop and mobile Linux, much less a centralized, unified Linux 'app store'. And as much as I endorse and enjoy the freedom and choices Linux provides, I'm really beginning to think that, given the direction things are going having the option of an integrated system is the only way Linux will make a major market impact beyond servers.

IOW, desktop Linux (i.e. Gnome, KDE,etc.) is still trying to compete with Win7 and OSX. Mobile Linux is gasping for breath. MS and Apple are preparing to unify their desktop and mobile efforts. IMHO, Linux developers must come up with a similar (hopefully superior) comprehensive effort if Linux has any hope of ever finally becoming a true 'mainstream' OS. No longer can mobile and desktop be treated as separate systems.