I released Excorporate 1.0.0 recently and declared the API stable. I was careful not to break API compatibility throughout Excorporate’s development so the API version stays the same at “0”.
The project is now in a state where it does everything I want it to do, API-wise. The UI is still missing features like meeting creation, but I just call the required Elisp functions when I need to, referring to the “API Usage” section of the Info manual.
I think there’s a lot of potential to create nice user interface features with Excorporate’s API — like a scheduler that shows people’s availability with ASCII-art bars, usable on a TTY. The included Org, diary and calfw front-ends show real-world usage of the API. I hope people send patches for new user interface features and keybindings, and contribute new authentication methods. I’ll continue watching for bug reports.