As a programmer, I selected "Updating" State: Partially pessimistic. It strikes a balance between the time I have to spend building it and the need to keep the user from leaving.
As a Trello user, I really like the way it updates the UI optimistically and makes it feel like everything is applied instantly, as if there is just magic instead of a back-end. It feel like it just works and sets my mind at ease, but most importantly, it provides a faster and less interrupted user experience. As far as I'm concerned, this is the kind of experience I want to provide to my users as soon as I have nailed down a good approach to achieving optimistic UI updates.