ArmA 2 Patch 1.05 Highlights:
* Free bonus campaign Eagle Wing
* Free bonus helicopter addon AH-64D
* New Warfare multiplayer mode When Diplomacy Fails, including 3-sides and support for diplomacy between factions
* Major AI tweaking and balancing (better combat cooperation, better situational awareness, new Suppressive fire command)
*Significant performance improvements, especially in large cities
* Fixed compatibility problems under Windows Vista and Windows 7 x64 with 8 GB and more RAM
* Grass now provides concealment also in distance
* Improved hit detection and damage system
* Improved object visibility and less significant objects popping in distance
* Improved mouse input handling
* Spatial sound improvements
* Automatic launching of user made addons (units, missions etc.) via “pbo” file association with the game
* Possibility to switch between windowed and fullscreen mode at any time in game menus using Alt + Enter or through video options
* Various crash opportunities fixed
* Linux server support added
* New GUI to various dedicated server settings
* New GUI for multiplayer commands
* Enabled commanding during story conversations
* FreeTrack support using FreeTrackClient.dll
* DRM free for users of legitimate installs
* Optional BattlEye anti-cheat protection
* Airplane Heads-Up displays reworked

In a recent interview Valve’s Robin Walker said:

“The primary change here is simply the decoupling of achievements and unlockables, which is the source of most of the negative feedback we’ve received around previous class packs,” said Walker. “It’ll provide multiple ways for players to get items, with a plan to add more over time.”

The full interview is very interesting and you can see the full version here. Including talk of the new sniper patch which would seem to be the next update.