The problem again is not really javascript, it is DOM manipulation. You can have the fastest javascript engine ever,if the bottelneck is the DOM , there is little you can do about it. And everybody doesnt own a quad-core mobile.

I like Titanium approach where the ui is native and the code is javascript,so you are basically using javascript with a specific API,not the DOM. I'd like to see more frameworks like this , or even , i'd like mobile os vendors to faciliate the use of their native framework with javascript, instead of having to use HTML5 in a webview for development. I believe that's what WP is doing. As much as i h*te MS , it is a good move.