Rated 5 out of 5 stars
To say that AutoPager makes this addon obsolete isn't just wrong, it's actually the complete opposite of the truth -- AutoPagerize made AutoPager obsolete.
On the surface the two addons do the same thing. However, for years now AutoPager has been one of the most notoriously bloated resource hogs in the world of web browser extensions. The developers even addressed this by releasing the "Lite" edition of AutoPager and, while it is streamlined somewhat and does perform better, it has all the symptoms of its parent extension only they're just less pronounced. The exception being that if AutoPager is the only extension or one of a just a handful of extensions installed, Firefox's performance is relatively unaffected. But that's not an option anymore -- this is an era of web browsing where most users have at least a dozen other extensions installed (sometimes dozens or even 50 or more).
Now... my goal here is not to bash AutoPager, it's to describe to you this extension -- AutoPagerize. And in order to do that you need only to imagine the polar opposite of everything I just said above about AutoPager.
AutoPagerize is lightweight, it plays nice with Firefox installations highly customized with dozens and dozens of other extensions, and has just enough configurability to keep it streamlined and not bloated. The only better option is possibly the AutoPagerize userscript for use with Greasemonkey, however, the developer of AutoPagerize has stopped development of that script in favor of developing it as a full-fledged extension for Firefox and Chrome. Though, it's worth mentioning that the AutoPagerize userscript is still available (http://userscripts.org/scripts/show/8551) and perfectly functioning (effective on ~95% sites in my experience) for users who value browser performance over all.