[bjourne]

Event-driven models work great when you have problems that can be modeled as series or sets of reply/response events or cycles. It does not work great when your problem is stateful, when minimum latency is important, when your problem is essentially one reply/response cycle or naturally sequential. The internals of a 3d engine should probably not be event-driven (the api might be, however). A program for listing files in a directory should also probably not be event-driven. Nor a program for computing solutions to differential equations. A text editor definitely should be event-driven.

That said, IME, event-driven architectures are more often than not the right choice for complex software. It's just a very intuitive way to model software.