To me, error analysis is the sweet spot for improvement.

The designer has an obligation to provide an appropriate conceptual model for the way that the device works. It doesn't have to completely accurate but it has to be sufficiently accurate that it will help in both the learning of the operation and also dealing with novel situations.

The design of everyday things is in great danger of becoming the design of superfluous, overloaded, unnecessary things.

It was always amusing to be inside Apple and read what journalists said we were doing

It is relatively easy to design for the perfect cases, when everything goes right, or when all the information required is available in proper format

Everything has a personality: everything sends an emotional signal. Even where this was not the intention of the designer, the people who view the website infer personalities and experience emotions. Bad websites have horrible personalities and instill horrid emotional states in their users, usually unwittingly. We need to design things-products, websites, services-to convey whatever personality and emotions are desired.

In my opinion, no single design is apt to be optimal for everyone.