A well-designed object or interaction should be —
Unobtrusive
— present & ready to use when needed, but not draw unnecessary, nonfunctional attention to itself.
Brilliantly Useful
— not only exceptionally useful, but exhibit its functionality in an invigorating or delightful way.
Environmentally Sound
— mindful of its place in the larger world, not wasting excessive resources.
Unique…
— able to offer something new, push boundaries, & stand out.
… yet Informed by Tradition
— at the same time, clearly aware of its place in a tradition, following established lines as much as possible & invoking expectations.
Encouraging of Creativity & Exploration
— aiming to augment the user’s ideas, push the user’s curiosity about the world, or teach something to the user.
Graceful in Failure
— readable, providing feedback to the user on what went wrong, why, & what can be done to fix it; if at all possible, don’t freeze, force a restart, or add weighty complexity. All things fail, but a well-designed object should fail gracefully.
Accessible & Affordable
— as accessible as possible to as many people as possible, without unduly diluting its features & quality.
Aesthetically Composed
— holistically beautiful. Each of its parts should contribute to the pleasure of the whole. As Aristotle says, every element of a work should be intertwined, so “if some part is moved or taken away, the whole is disturbed & destroyed” (Poetics 1451a, my translation).
Inviting & Intuitive
— as easy to use as possible, without reducing required operational complexity or power, while also seeming easy to use from the outside; built to require as little introduction as possible, standing on its own terms & usable in its own right.