In the up-right corner of the website, you will find a link to Behind the Scenes developer section, where I found some interesting notes:
We think that the HTML5 version makes the web more fun and it demonstrates the advances in standards support made in the latest version of Internet Explorer. With that in mind, we want to share some of the cool “behind the scenes” technical details used on this project to help you build your own HTML5 sites and ultimately get ready for the Windows 8 Store!
Regarding performance, the developer section shows a comparison table with the average framerate on some different systems.
You can see that you can get almost the same Framerate whether using Win7,i7 CPU and 8GB RAM and a Win8,i5 CPU and 4GB RAM. But wait! RAM “quantity” is not really important, nor CPU speed. I think the most important component to compare here is the GPU (a lacking column in this table), namely the GPU Clock Frequency and RAM, that have much more influence in FPS than the aspects shown here, so I’d like to see some independent tests and comparisons between Browsers on the same system (like they did with Windows 7 here, but with different systems, which will obviously change the results).
Finally, here is the video on the dev page on YouTube.