It would be nice for someone who thinks they will be using C++ to write Metro Apps to chime in and tell me what advantage you buy. Dont tell me portability or you cannot learn C#. I think you guys are hitting the nail on the head that .NET is legacy. This story is still fuzzy right now.
Here's one... as for the advantages, let's just say that C++ is the stick shift of computer programming
Seriously, it's a matter of personal preference and of being able to use the right tool for the job. Or at least one of the right tools for the job. It's also a matter of welcoming as many developers as possible to the new platform, letting them use their weapon of choice.
Might not work as intended, but I think it beats the "Objective C only, please" kind of policy hands down.