Good design is utterly unsurprising, except when it lets you do something more easily than you expected. Good design is something you don't notice has been designed at all, because it works exactly as you expected it to. Good design is like a comfortable old jumper. Good design is simple. A single good design eliminates whole fields of gadgets, widgets, and gizmos previously necessary to do the job. Good design appears effortless, looks trivial. Good design is not cool. Good design fades into the background. Good design does not demand your appreciation. Good design does not cause psychic stress.
As Donald Norman is wont to say, good design doesn't win awards. The really killer designs cause paradigm shifts, they do things we used not to have categories for but now think trivial, and are thus invisible. Or their brilliance operates on levels below conscious awareness, so that we only know that it feels right but can't point to any particular cleverness to explain why.
Another thing about good design is that it shouldn't be perfect, which is where most designers go astray. The best designs incorporate an element of randomness into their process of creation so that each item has a unique character. A thing that has a perfectly smooth form, blank surfaces, sharp corners, will show up every dint. You can't be rough with it, it has to sit in a display case rather than becoming part of your life. You won't be able to add things to it or remove things from it without it looking goofy. Eccentricity, imperfection, random texturing, besides having a comfortable human feel, allow a thing to be added to without those additions also having to be precise. Good design affords extension and play.
A thing should not hide how it was made. A veneer just leaves you wondering what hidden parts could fail, causing psychic stress. Good design has to go to the core. A good design requires and reflects a simple process for constructing the thing. Good design is not achieved by endlessly refining one thing, but by endlessly tweaking the process by which the thing is made. It is achieved by first failing a thousand times. It will be obvious how a well designed object was made, yet mind boggling that someone would think of making it that way.