There are many state machines where you need to execute an action on entry into that state. This is especially important for more complex state machines where there may be multiple transitions (from different states) that go into a particular target state. In those cases, you would end up having to write the same code in multiple transitions, which makes maintenance more difficult. Instead, an _entry (or other reserved) action would allow the actions to be consolidated to one place. This also applies for when exiting a state.

I've been able to implement it quite easily (not sure if it is completely correct, since I am bypassing the middleware layer).

What are your thoughts?