Counter-Strike Global Offensive has been available in beta form to select users on Steam for quite some time now, and it's getting a huge update today.
The update has been the largest for the game to date, and is designed as a part of "an even larger update" which Valve plans to release shortly.
In addition to the usual weapon tweaks and balances, the new update allows 30 players (15v15) to go head to head in official maps. Burst fire has also been revamped, and bullet tracers have been added to existing weapons.
Players can soon expect to play on even more official maps when the larger update is released in a few weeks.
You can read the full changelist for the update on Steam here.