A new map and competitive FFA mode to go along with it are the biggest additions to Overwatch with the release of the games 2nd-year anniversary update.  Posted just hours ago, the patch notes starts off with a special word from Lead Designer Jeff Kaplan:

Holy cats—it’s hard to believe it’s been almost two years since the release of Overwatch. As you might imagine, this patch is all about celebrating that milestone with the people in our community who made it possible. We’re marking the occasion with a ton of new content, including a new map (plus our first-ever Competitive FFA Deathmatch mode), but one of the most exciting parts for me personally is that for the first time ever, we’re making nearly every one of our past seasonal brawls available for play again at some point during the event in a sort of “greatest hits” marathon. I’m looking forward to teaming up with all of you for another round of Mei’s Yeti Hunt and Junkenstein’s Revenge. If you see someone on your team wearing a XX skin and spamming the XX emote, that’s probably me. Sorry in advance for zeroing you out at Lucioball. 

Getting more into patch specifics, we see buffs to Ana and nerfs to both Brigitte and Hanzo. Hanzo has, expectedly,  received a nerf to Storm Arrow damage, and Brigitte's Shield Bash cooldown has increased by one second. In addition, her Rally ultimate ability now grants 50 less armor.

The Ana buffs are refreshing and, hopefully, will allow skilled Ana players to rise above the other support heroes that heal more damage much easier. Now, Biotic Rifle shots will pass through allies who have full HP, a huge buff that makes holding certain chokepoints and defending with Ana much easier. She also has 4 more shots per clip before she needs to reload -- all things that will help Ana heal more often and more consistently.

A new competitive Mode

With the popular FFA Deathmatch mode now being a competitive option for players, many are rejoicing at the ability to earn competitive points without having to slog away in 6 vs. 6 environments. Equipped with "placement matches, skill rating,  and leaderboards" the mode will likely be very popular. One can imagine popular streamers and pro players enjoying the mode immensely, as the introduction of a competitive mode has a way of raising the quality of matches significantly.

You can read more about the variety of bug fixes and details in the official patch notes here. Although they were leaked days before the official release, the newskins in their full high-res glory look great!