My gripe is the disappearing header that reappears at the slightest twitch of reverse scrolling. The behavior needs to work more like drag down to refresh: only reappear with a deliberate and significant scroll "up" (a drag down with the finger) or just stay at the very top where it belongs (it only takes one tap on mobile to get back there).

With most of them if you need to backtrack and read a few lines up, you have to scroll well past the point or the exact text you want to read gets covered by the header.