Developers who submit a Windows 8 app to the Windows Store using the word 'Metro' will "fail certification". This is a move from Microsoft that will see the Metro name die a horrible, horrible death. A recent change to the "Naming your app" instructions appears despite the heavy use by Microsoft of the term elsewhere.
This means that developers are now having to rebrand their apps in order to pass the new, stricter, non-Metro requirements. One big example is Windows-based Twitter client, MetroTwit, which already has a great following, and it now risks losing users when they go through a now required name change.
This is a big change, and its getting so close to the launch of Windows 8 I fear the Microsoft may be poisoning the Windows 8 name by this huge tectonic shift in renaming Metro, and the domino effect its having on developers, and their apps. Time will tell, I guess.