Why? Well, because it’s optimized to run on your Android or iOS device. Head on over to the demo and try it out. Of course, it’s not the full extent of the OS, but they are focusing on the main stuff. Texts, People, Groups, Phone, Calendar and Local Scout.
I suppose the point isn’t to show you the apps (those are here, by the way, but rather how you navigate through the phone, as all apps (except games) use the same navigational and graphical schemes.
Honestly, as much as I’d love to fill the rest of this side of the article with text, it would be boring filler. So go try it out, from your phone.
Edit: As silly as it seems, I can’t try the demo on my own phone, a WP7 device running IE9. The browser isn’t supported. Yet it works in Chrome. ಠ_ಠ