I'm surprised that they emphasize the fact that the keyboard can be invisible or small. Personally I think that's the most confusing feature because it leaves you tapping on the screen, or website as in the video. That aspect to me is not very intuitive as to whether or not I'm typing currently or trying to navigate the website by tapping a link, etc. Also, if it's invisible, how do you know when the keyboard is brou…
I imagine it'd be possible to detect that you've got all of your fingers resting on the screen in the 'keyboard' configuration, and only 'activate' the keyboard when that's the case.
Like how with an iPhone it can distinguish when you press and slide your finger to scroll from when you press your finger to tap a link.
I think it'd be a cool feature because it'd give you so much more screen space for visible content (like when you're editing a document), and less of the context-switch that happens when an on-screen keyboard pops up.