Regarding minimaps: I thought, these were great, too, but then I discovered that I find them rather irritating and that I actually don't use them. I guess, this is, because you have to maintain a mental mapping of that document and how it is organized, already, for the minimap to make sense. But, then, referring to that visual mapping of what you're already mapping in a much more abstract sense, seems – at least for me – to be rather adding friction than being helpful.

The scrollbar, being both highly abstract and visceral/tangible at the same time, is hard to beat.