How does AutoPager work with sites (such as certain hardware review ones) which paginate content above the fold? I.e. how can it tell when I've finished reading and need to page?
AutoPager does an optimistic pre-fetch of extra content, meaning that while you're reading page 1, it's loading page 2; once you hit page 2 content, it begins fetching page 3, etc. It's likely a bit more complex than that, but ideally, with AutoPager in effect, you shouldn't ever realize you stopped reading page 1. :)
If you use Firefox, I highly recommend it: https://addons.mozilla.org/en-US/firefox/addon/4925