The first thing I do when I work in an editor with a mini-map is -- turn it off. I find it mostly the most useless feature for coding, and for sites it seems to be equally useless. Why?
1. Stuff is too small to really make out where I'm going or navigating.
2. Short or long pages, both don't really benefit from the loss of screen real-estate. Or the distraction really.
3. Other tools like a proper index with descriptive headers, or the search function work so much better to navigate the page.
Where mini-maps could be awesome are large images, or maps. They tend to visual in nature, and when zoomed in you can look at the mini-map to see where you are in the whole. Which is useful.
So, cool future, but this doesn't really seem like a great implementation.
