IE NetRenderer allows you to check how a website is rendered by Internet Explorer 9, 8, 7, 6 or 5.5, as seen from a high speed datacenter located in Germany. Just type in a URL in the field above and try it out - it's free!
Is HTML5 video ready for prime time? I can't give a definite answer to that question - but I can say that getting it to work cross browser, and that includes the iPad can be annoying.