One of the features LG pushed hard with the announcement of the G3 was its Knock Code screen locking feature. While the device is asleep, you can tap on the screen in predefined locations to wake it and unlock instantly. Knock Code actually debuted on the G Pro 2, but now Sprint's G2 is getting it as well.
The update (with the odd version "ZVD") is beginning to roll out today and is coming in stages. If it's not available on your phone right away, give it a day or two. You're welcome to mash the update button relentlessly, but no promises.
The addition of Knock Code is the only thing listed on the changelog, but the G2 has gotten plenty of love in the past. Sprint updated the device with Spark LTE support back in January and bumped it to KitKat in March. Sure, the international G2 got Knock Code in April, but this isn't bad for a US carrier.