When I read a subscription on Google Reader, Google just-in-time loads more entries as I reach the bottom of the page. It would be nice to have the SO sites do this too instead of having a pager on questions with lots of answers.
Okay, but first you have to install Firefox and Greasemonkey.
Pagination is in my opinion much better then progressive loading. Progressive loading breaks both the scrollbar and the back button.
The problem with pagination is that it breaks the browser's Find function; however, progressive loading does not fix this issue either. (We'd need a "view all" or "print view" option.)
For SO, I actually prefer paging. Other sites like DZone use this auto-scrolling behaviour. I guess to seem more app-like than Web-like but honestly I tend to just find it annoying and unnecessary most of the time.
Paging makes it easy to get to the last page or even to a specific page (not often used but sometimes it is).
I do think it works for Google Reader but you'll note that others like Gmail use traditional paging.
Here is a UserScript that does exactly that. Enjoy!