ArmA 2 will be largely compatible with Armed Assault. To make porting of content from ArmA as simple as possible, there are few important things:
initJIPcompatible.sqf initJIPcompatible.sqf gets called from the MP mission framework (scripts in modules MP directory). A script waits until the player object is initialized and execs initJIPcompatible.sqf on clients (all clients, even those that were allready there at mission start as it is basically the same). Has nothing todo with init.sqf.
Multiplayer Dedicated server broadcasting to all clients.
Some Code optimization tips.
Zone Markers creating script for warning zones.
IED usage improvised explosive device usage through script.
Few more Scripting command reference items.
Common scripting errors help you to debug your code.
Group in Vehicle check.
BIS_fnc_spawnGroup how to create whole groups from CfgGroups class.
BIS_fnc_findSafePos how to find safe position with open ground etc.
Global scripts dir or common scripts dir is very useful. This feature has been known since OFP, check out the details from ArmA: Scripting - Global scripts dir, as same feature works in ArmA 2.
Howto create and use Object Compositions in missions.
enableSaving and why its useful to disable.