I have some APIs I have to call that take up to 5 seconds to return and resist caching (hotel availability, for instance). Would those delays become even more jarring with an approach like this?
For instance, take gmail. Some part might hard to use that way.. for instance, chat communication where you somewhat need to receive the answer of the other person to show it. However, adding labels, deleting a message, etc.. that can all be made asynchronously.