Rated 4 out of 5 stars
I decided to give AutoPager another shot after running into issues with my long-time favorite paginator, AutoPagerize, and I'm glad I did.
The key feature here is AutoPager's 'Lite' mode. Now, while 'Normal' mode will paginate just about every web page out there right out of the box, it uses a "brute force" method of checking each page against a huge list of pagination rules which, ultimately, makes Firefox sluggish due to greater RAM/CPU usage. (In fact, AutoPagerize takes the same approach and has the same issue, and it's one reason why I sought an alternative in the first place.) It's not a horrendous performance hit, but it is noticeable.
However, with 'Lite' mode, you start with a clean slate (i.e. no pagination for any site) and then chose which sites you want AutoPager to paginate as you go. For example, go to Google, click the AutoPager icon to see a list of rules for Google search, choose a rule to install and, from there on out, Google search results will always be paginated. Want pagination for your favorite forum, but not for Facebook? Then install the rule for your forum and skip installing any rules for Facebook. Or install a rule for Facebook but disable it in AutoPager's rule manager so that it's has no affect for now but is there in case you might want it later. This method of selectively installing/enabling pagination only for the sites you want significantly reduces the amount of RAM/CPU that AutoPager uses and keeps Firefox performing nicely -- even when you have dozens of tabs open at once.
The only downside is that the name 'Lite' might be misleading. 'Lite' mode certainly is light on your computer's resources, but it's much more complicated to use than 'Normal' mode. Beginner-level Firefox users will likely be at a loss and users with even an intermediate-leaning understanding of web browser and web pages may find 'Lite' mode to be a bit too technical and too much work. (Then again, that's what 'Normal' mode is for -- anyone can use it and the performance hit is acceptable during simple/routine browsing activities.) In addition, the issue of complexity is further compounded by the fact that AutoPager's interface (addon config, rule management, etc.) is somewhat lacking when it comes to being organized and intuitive. And this is why I rate the addon 4 stars instead of 5.
Ultimately, though, once you get past the quirks and get a feel for AutoPager's overall system, it's well worth it. Pagination is a very, very handy feature to have in a browser, and AutoPager provides probably the best all around approach for making it work.