I'm mostly a fan except for the broken scrolling behavior.
Web developers, it is not OK to mask a big chunk of horizontal scrollable space with a toolbar header thing like that. This breaks page up and page down scrolling (from the keyboard or clicking in the scrollbar trough.)
With your implementation, when a reader reaches the bottom of the page and then pages down to continue reading, he will lose a couple of lines of yet to be read content under that big toolbar header thing.
If you must have a toolbar across the top, move the scrollable areas of the page below it. It's not that difficult to not break such a basic navigation tool as page scrolling.
