PageZipper (http://www.printwhatyoulike.com/pagezipper) also automatically adds the 'Next' page to the bottom of the page you're on. The cool thing about PageZipper is that it's insanely simple to use- you just turn it on. PageZipper locates and adds the next page entirely automatically, so you can focus on what your reading instead of mucking around with selecting links or editing xpath expressions. PageZipper also provides a way for you to navigate through any online image gallery using keyboard shortcuts. Check out the video to see how it works.

Anyone that tried them both care to opine which was better?

I've been using this for quite some time. The best part is that it downloads people's rulesets for paging sites, so 99% of the time you don't have to set it up yourself.

I'm also a satisfied user of this extension. I find it particularly interesting as an example of how crowdsourcing can work not only for posting news, tagging photos, etc, but also for contributing simple code snippets which find the "next page" link.

The scroll for Hacker News is a bit ugly. For a cleaner effect that doesn't strip page style, change the "Content XPath" to:

/html/body/center/table/tbody/tr[3]

I've been using this for a few weeks now, and (besides AdBlock Plus) this is the most useful extension that exists for Firefox.

This is becoming the coolest firefox extension I use. Works great on sites like google and flickr too.

Is it just me, or should this be a GM script, not a full-fledged extension?

This is sweet!