UE3 - UDK Simulated Functions

The point in using simulated functions can be derived directly from the meanding of that keyword: "Functions that are called in the context of an actor will not be executed if the Actor's local Role (not RemoteRole!) is less than or equal to ROLE_SimulatedProxy unless the function is declared as simulated or as native."

In other words, if you have a replicated actor and e.g. implemented the event Tick() in it, that event is always executed serversidely. Whether it is also executed on the client depends on the clientside Role (= the serverside RemoteRole) of the actor and whether the Tick() function is declared with or without the simulated modifier. Almost all replicated actors have the clientside role ROLE_SimulatedProxy, so they only execute functions that are declared with the simulated modifier.

Cases when using "simulated" would be pointless or redundant include classes not derived from Actor, static functions (no actor context in both cases!) and Actors spawned clientsidely (as opposed to spawned serversidely and replicated to a client), such as the HUD. Also, it is completely pointless to declare any functions "simulated" if the actor never leaves the server (e.g. GameInfo) or always has the role ROLE_AutonomousProxy on the client (PlayerController - only exists on the server and owning client).