I stumbled upon a FireFox extension (http://nextplease.mozdev.org/) that does what I've always missed from Opera – the ability to go to next page page in Google using keyboard shortcuts alone!

YES!!

The idea is, you use the space bar to scroll down a search result page, and when you hit the bottom, just hit Ctrl+Space (I mapped this key extension using NextPlease) and voila! The next page loads. Uber cool.