Windows Phone 8.1 is crazy long, so we'll just hit the top of the list. Number one, of course, is the aforementioned voice assistant, which will allow you to perform a wide range of tasks, like setting reminders, alarms, searching the web, and more. Another nice change is the addition of the Action Center, aka the notification tray with quick settings toggles. AT&T's announcement also claims that the update "takes full advantage of the Lumia 1520’s Quad-core processor, large, bright 6-inch HD 1080p display, and Nokia Rich Recording suite – four digital microphones and 140 dB recording range", but it is unclear if that means any more than that you'll get better sound when recording.The list of updated features in
You can wait for the update to hit your device at its own speed, or you can start obsessively checking for the update by going to Settings-->Phone Update, and manually checking. The update will still be at the mercy of the rollout, but you might catch it a bit sooner that way. If you loaded up the WP8.1 preview, you may need to downgrade in order to get the update, so we've put together a how-to for that.