Appointments can be written directly on the line next to a time. The address book opens an entry window, but the note is accessible from the list view. Todos can be written directly on the main screen. The memo pad opens a window. In addition, a new entry can be started just by writing in the Graffiti area in the built-in apps.
Letters start a new description in the appointment book, numbers launch the time picker.
Letters jump to that entry in the address book. Letters start a new todo or a new memo in their respective apps. Third-party apps vary in their paradigm. And sometimes the Jot area pops up when I don't need to do text entry. There has been a lot said about the difference in resolution on the two operating systems.