I'm surprised that pdf.js is described as a "success". I don't think I've ever heard a user of it say anything good about it. Any time I have heard about it, it's always somebody else in the office cursing loudly about it taking forever to open a PDF, or that it locked up Firefox, or that it's rendering something improperly, or that they wanted Foxit Reader or some other app to open the PDF instead of Firefox. Just because it's integrated with Firefox doesn't make it a "success", as far as I'm concerned. Australis is bundled with Firefox, too, and it's almost universally hated.