I don't see why this debate continues to rage on - it has no meaning in the context of reality... It's been made very clear - beginning at BUILD 2011 - that this is not about This vs That. You use what you know how to use, what you want to use, as it relates to HTML5 and Windows XAML for building Windows Store Apps.

Please watch http://channel9.msdn.com/Blogs/Bytes+by+MSDN/Bytes-by-MSDN-Windows-8-Design-Tools and start building apps in HTML or XAML, whichever you prefer!