We knew ahead of the iPhone 5 keynote that iOS 6 would take advantage of extra pixels on the iPhone 5 (640-by-1136) in order to render an additional, fifth row of icons. What we didn't know (but kinda expected) back then was that the per-folder app limit in iOS 6 running on the iPhone 5 would be raised from twelve to sixteen apps.
Strangely enough, even though Forstall and Schiller made a passing mention of this improvement during the unveiling, Apple's iPhone/iOS pages and the official 155-page iPhone 5 User Guide never detail it.
Now, I'm sure there are better ways to take advantage of those 176 extra lines, but if you're managing the home screen madness by organizing apps into folders, you'll quickly learn to appreciate this little nice-to-have which helps reduce the home screen clutter on your device...