Something useful I just noticed:
You can use DialogDisplay inside GetLocalPlayer-blocks, and the clicked dialog button will be registered by all players.
Why is that useful? Because with this something local can trigger something for all players.
I use this for menus for observers. Because almost no events register what an observer is doing, I simply tell them to move their camera to one of the four corners of the map to trigger a menu.
This is an example for the kick menu, which will display when the admin-player moves his camera to the bottom left corner of the map, and waits there for 10 seconds.
Before I had this, I was using a simple "-kick x" system. And that would not work if the admin-player was an observer. This does :).
I have only tested this on LAN with 2 players, but I don't see any reason, why this wouldn't work over Battle.net, or with more players.
Maybe someone else can find some other uses for this. Maybe to sync some information. (I can't think of a way to do this, but maybe it's possible) I just wanted to share this.