This may all look great however there is something really important that one has to realize before writing any code that depends on the event system: the system must be _complete_ in order to be useful for a production-grade development. E.g. if one gets an event when opening a document via File->Open and doesn't get it when, say, running an action that opens a document, or if an event is triggered when user uses a specific tool but is not when the user performs an Undo, this pretty much makes any plugin development that simply monitors the events and does something useful, in a reliable way, upon certain type of events, a truly futile enterprise. It's impossible to tell the user what actions they can and cannot do for the system to perform properly; moreover, one cannot even warn the user they are doing something unexpected because, well, no events are triggered in such case.
So before getting too excited about it, if this system relies on PS events as they can be parsed by a C++ "listener" plugin as of CC2014, the event system IS in fact incomplete and therefore cannot be solely relied upon for all document life-cycle events. Just FYI.