@cbae: Well, yes, it's hard to build large applications with modularized components in JS... That said, that has little to do with building a Windows 8 Metro style app in HTML5 (HTML, JS, CSS3, etc...). JS is rife with libraries that you can use in a Metro app (like jQuery for the most obvious example). Building apps should not be defined by the need to build structured code architectures, just as you don't have to write statically typed OO to write a Metro app.
You're missing the point. If you are an HTML developer, then you already know the idiosyncracies of the tools you use (so, HTML, JS and CSS). You're not forced into making your JS Metro application look like a .NET application. Where are you getting these ideas from?
If you're not an HTML developer or proficient in JS, then why are you worrying about this stuff? Use what you know. Most importantly... Build an app! Give the plaform a spin. Come on.
C