Officially coming out April 9th, 2007 at 7:00 PM Eastern
Here are more details for the upcoming update straight from the Microsoft email,
In Annex, gamers seize victory by keeping control over key map locations, or objectives, long enough to collect a winning number of points. Every map contains two to five identified objectives available for capture, with one objective active at a time. Objectives are based on map weapon-spawn locations and have a potential value of 60 points toward either team's score. Teams collect those points by maintaining ownership of an objective until all 60 points have been distributed. Every second that a team controls an objective, the team gets one point. When an objective falls to zero points, the next objective is selected at random.
VGA Cable Support: Monitor resolution widths greater than or equal to 1280 now render as letterbox. In particular VGA users running at 1280×1024 will now see the game in full 720p (1280×720) resolution in letterboxed form.
Adjusted Assassination Multiplayer Gametype: Leader no longer has to unlock weapons and now has to be executed to die.
Adjusted Boomshot: Splash damage to be more effective rendering targets down-but-not-out
Adjusted Hammer of Dawn: Aiming will be more forgiving of moving targets
Adjusted Roadie Run: Reduced frequency of accidently grabbing cover while running
Kill Message Ticker: Ticker can now be seen while down-but-not-out and spectating
General: Addressed a number of possible exploits in multiplayer