UPDATE: Playing with it a little more I do think it is a little flakier than that. There's something weird about the marquee image that makes the header re-appe

UPDATE: Playing with it a little more I do think it is a little flakier than that. There's something weird about the marquee image that makes the header re-appear for reasons I don't understand. If you use the arrow keys for scrolling (so there's no chance of an accidental "bounce" when you stop moving your fingers) the behavior is a little more obvious and consistent, but you can see that when scrolling from the top of the page the header disappears then comes back briefly for reasons that aren't clear to me. Clever or subtle UI/UX behaviors on the web are hard.