I like this project. I sometimes feel Chrome has a slight advantage because Google is also building really cool services, so they can get both sides in sync (e.g. returning WebP images in page previews, or encoding to WebM with Youtube).

By building things like Pdf.js and butter/popcorn.js and giving them away for other projects to use Mozilla gets to have the same impact and feedback loop, which helps to further their mission to improve the web.