This has been a long time coming. I am happy to see the implementations of HTML5 technologies that are capable of delivering this kind of experience.
The scrolling was jerky for me on my newish desktop PC. There doesn't seem to be any new "technology" here, just some slow wrappers around stuff that was around years ago. If this is being touted as "the future" then programming is really going down the toilet.
1) security 2) computational performance 3) flexibility
WebSockets for example are just a bad rehash of existing APIs. Woopty-doo.