There's a new patch out for testing on the Overwatch public test realm today, and while not the most important change, the new sit and laugh emotes seem to have had the biggest effect on fans—namely D.Va's new 1,000-credit emote in which she plays a videogame while eating chips (D.Vas, but they're Doritos) and drinking soda (I'm going to call it Mountain Dew).
As far as balance goes, the test patch reworks competitive play ahead of season 2, changing skill rating to a 5,000-point scale made up of six labeled categories, Bronze, Silver, Gold, Platinum, Diamond, Master, and Grandmaster. Although this is a significant change from Overwatch's existing 100 point scale, it's interesting that it represents a compromise between assigning players generalized categories (as CS:GO does, for example) and ranking players with a granular, numerical skill rating that arguably encourages them to grind.
Other big changes include the removal of sudden death and the addition of draws, and an adjustment to how tiers are lost.
Nine characters have seen changes as well. Those with nerfs include Lucio, whose movement speed boost was lowered, and Zenyatta, whose Orb of Discord is 20 percent less effective. However, Zenyatta's Orb of Destruction has had its damage increased from 40 to 46, and Blizzard notes that "the amount of damage that he delivers should feel largely unaffected by the change."
Some interesting changes have been made to Genji: His double jump no longer resets when wall climbing, and Junkrat's steel trap can now catch him mid-dash. He's also had two seconds shaved off of his ultimate duration.
The biggest buff goes to Mercy. Not only does her beam heal 20 percent faster, three-quarters of a second has been trimmed from the time it takes heroes to become mobile after she resurrects them.
You can read all of the patch notes on the official site, and try out the changes by selecting 'PTR: Overwatch' in the Region/Account drop down in the Battle.net launcher. Below I've embedded a video by Seba showing the most important thing about the update—all the new emotes.