I was disappointed with AT&T not providing the Android 4.1.2 update when other US-based carriers made it available, especially since we got the 4.1.1 update pretty early. Even more disappointing was when this was finally available - around the beginning of August - my device never upgraded. A Google search the other night showed it was available and when I manually checked for updates - sure enough, it was.
I will say I'm pleased with the update. Multiwindow is pretty cool even if not standard. It doesn't support all apps - and even some common ones I use that would be nice to use in multiwindow mode - like Google Keep.
The best part is that IPv6 now seems to work! At least over WIFI. I have IPv6 running at home and was (again) disappointed when my wife's iPad and iPhone could get to IPv6 sites and my Android couldn't. But after the update, I tried What Is My IPv6 Address from my Android and got an IPv6 address back (you'll see your IPv4 address if IPv6 isn't working)! I confirmed with my favorite IPv6-only site Loops of Zen.