Is the product capable of allowing people to learn, carry out their work efficiently, access the information that they need, or buy the goods, that they want?

Once users have learned how to use a product to carry out their tasks, can they sustain a high level of productivity?

Does the product provide an appropriate set of functions that will enable users to carry out all of their tasks in the way they want to do them?

Is it possible for the user to work out how to use the product by exploring the interface and trying certain actions? How hard will it be to learn the whole set of functions in this way?

What types of interface support have been provided to help users remember how to carry out tasks, especially for products and operations they use infrequently?