@JoshRoss: The problem I see is that what people expect from a Windows 8 app is not what they expect from a website. If you don't want to go for the least common denominator, then I'm not sure what JS would buy you in this case unless, of course, you are so familiar with the language that it would cut significantly your development time.

Every version of Windows sold big, even Vista the terrible, even Me the blue-screener. Regardless of what we think of it, Windows 8 is going to be a huge platform, huge enough that comparing it to some fancy flavored vodka is not the correct simile IMO. Try coffee... yes, you can drink it in nondescript paper cups, but there's a huge market for ceramic mugs.