The patch 1.04 will mainly solve and improve/balance the following in-game issues:

Major

* Mouse controls: Improved mouse handling and responsivness
* Stability: Fixed CTD caused by Voice Over Net when many players were speaking simultaneously and other stability problems
* Sound: Fixed speed of sound simulation and other improvements
* Multiplayer: fixed scoring, multiple mission parameters added and various other MP-related improvements

Engine:

* New: Added mouse smoothing to game options.
* New: Enabled multiple parameters for MP missions.
* New: Mouse filtering strenght adjustable using mouseSmoothing=NNNN in user config.
* New: Command line argument -cpuCount=NNN to override cpu count detection.
* Improved: Mouse smoothing disabled for fast movement.
* Improved: Mouse smoothing can be disabled in user profile file using line mouseSmoothing=0;
* Improved: Audio volume settings.
* Fixed: Soldier were walking on non-existant heaps of debris from destroyed buildings.
* Fixed: Autocoordination caused rudder oscillation in high speed flight.
* Fixed: Crashes in VoN when many players were speaking simultaneously.
* Fixed: Immortal freezed soldiers occured in MP.
* Fixed: Broken kill scoring in MP (two points for unit kill).
* Fixed: Input key actions are no longer active while chat mode.
* Fixed: Diag_log used with long text argument caused crash.
* Fixed: Mouse scrolling in diary.
* Fixed: Enemy kills made by player using stolen enemy vehicle are no longer considered as friendly kills.
* Fixed: Switching to Utes from Chernarus caused Utes to contain infinite landscape.
* Fixed: Time of day synchronized on client after connection to server.
* Fixed: Speed of sound simulation.
* Fixed: Fire from rifle distort sound.
* Fixed: Crash by malformed input to a diag_log scripting function.
* Fixed: Dark muzzle flash in some of the weapon optics.
* Fixed: MP: Ships and boats used excessive bandwidth and CPU power.
* Fixed: Players are no longer forced to reconnect after MP Load on server.
* Fixed: Bike rider can be no longer healed.
* Fixed: Sometimes crew of a near vehicle was visible through the vehicle.

Missions:

* Improved: Communication menu updated to work with the new menu systems.
* Fixed: Some persistent RE calls added for better JIP compatibility in campaign.
* Fixed: Music was sometimes not playing properly due to faulty playMusic RE command call.
* Fixed: Scene area cleared from exploding destroyed vehicles during various scenes.
* Fixed: Possible appearance of immortal non-player characters in campaign.
* Fixed: (First to Fight) MP: Logos shown on client every time after JIP.
* Fixed: (First to Fight) MP: Skeet shooting not working for clients after JIP.
* Fixed: (First to Fight) Players not boarded in the chopper if they got in the towing tractor.
* Fixed: (Into the Storm) MP: Bad position of client players during converation.
* Fixed: (Into the Storm) Some voice-subtitles difference in the first dialog.
* Fixed: (Into the Storm) MP: No callsign for HQ entity on clients.
* Fixed: (One Week Later) MP: Clients not sitting on bikes after leaving the AAV.
* Fixed: (One Week Later) MP: Player is no longer the co-pilot in the Osprey.
* Fixed: (Manhattan) Escort chopper often shot down.
* Fixed: (Manhattan) Palyer stuck in the animation after first scene.
* Fixed: (Badlands) Prizrak no longer initiates conversation if Cooper is in a vehicle.
* Fixed: (Badlands) Non-fucntional ending in campaign scenario.
* Fixed: (Missing in Action) Redundant random sentences from Razor.

Modules:

* Improved: Ambient Civilians module caused lag in MP due to window lights.
* Fixed: Undefined variables in Ambient Civilians module.
* Fixed: High Command could behave strange when someone added his own display event handler.
* Fixed: Wrong positions of objects/logics.
* Fixed: Performance problems related to Animals module in MP.

Data:

* Improved: Some of the vehicle HUDs now contain missing info.
* Fixed: Alignment issues on several wrapper UI screens.



System requirements:
ANY ORIGINAL VERSION OF ARMA 2 from 1.00 to 1.03 other than Steam version, Steam users should use auto updating feature instead (their game will not be playable if they applied this patch until they recover it again from Steam)
DirectX 9 March 2009 is required and should be updated during the patching process automatically as needed or you can update your version of DirectX from www.microsoft.com/windows/directx/