General
FSX: Steam Edition is now built using the VS2013 compiler for better optimisation and performance. (Still makes use of VS2005 libraries for backwards compatibility.)
Updated splash, launcher and mission preview images for FSX:SE versions.

Multiplayer, networking and communications
Gamespy networking now replaced by new Steam networking.
Game chat now integrated with Steam chat
Friends/Banned lists now integrated with Steam.
Game invites now use Steam.
Host networking defaults to a single port 6112.
Host networking uses 27016 for Steam Master Server Browser.
Host timeout (loss of connection to host) now 35 seconds by default (was 55).
"Disconnected" message dialog now retained on screen for 4 mins before automatic dismissal (was 30 secs).

Steam Support
Top Down Camera (camera view select 4) was previously bound to F12 by default which is normally used for Steam's screen shot feature. Camera View Select 4 now uses Shift+F12 by default to avoid potential clash.

Compatibility with FSX boxed
FSX and FSX: Steam Edition co-Existence feature allows both versions to be installed on the same machine.

Default System-Setting Alterations
Increased TEXTURE_MAX_LOAD to 4096 up from 1024
Changed HIGHMEMFIX=1
Increased Vertex and Index Buffers and the number of buffers.

Bugs Fixed
Fix to particle emitter controllers which were not being updated properly.
Fix to flush all levels of detail in terrain cache.
Fix to Texture Composition preventing fail and crash.
Fixed issue where player is able to reserve more slots for friends than maximum players allowed in the game.
Fixed issue where invalid Briefing Room was presented to player when cancelling session creation.
Fixed issue where weather text in the multiplayer briefing room is partially cut off.
Fixed issue where no error message appears when attempting to host a session with the network adapter disabled.
Fixed issue where there is no error message when attempting to host a session with the network cable unplugged.
Fixed issue where host player is frozen after a collision occurs in multiplayer.
Fixed issue where client gets dropped from a multiplayer game after they crash into the host.
Fixed issue where the Host Options in multiplayer/ Free Flight allow a user to have a maximum of 99 player slots.
UIAutomationCore.dll work-a-round is now supplied by default with FSX:SE. This fixes a number of crashes relating to UI interaction on 64-bit versions of Windows.
Fixed issue where the application's taskbar preview window displays no content on Windows 8 and above
Prevent default colour mode for Windows 7 and above (enable automatic display composition).
sserife.fon file now automatically supplied and loaded.