It's really great for ingame sequencing of events. For instance things like trigger zones for player's reaching a spot and triggering a change in the GUI, or activating the next sequence of stuff to continue the tutorial because basically the player is working through "states" of the tutorial or guide, so the tutorial is just a big FSM, essentially.
You can communicate between scripts and playmaker FSM's pretty easily if you need to with this sort of thing, too.