The Composition of a Good Design

We live in a world where we are surrounded by design, from the toothbrush we use to brush our teeth to the style of font in which these words appear.  I was recently told about the documentary Helvetica and it got me to thinking about design and what makes it so effective that it can become nearly timeless.  One thing I found interesting in the independent documentary about typography and graphic design is how Massimo Vignelli compared the composition of typography to music, "it's the space in between the notes that makes the music" and the same rule applies for typography.  Design is a powerful element in our world, it can set the mood and the atmosphere, not only affecting us physically, but mentally as well.  I recommend watching Helvetica, especially if you are of the creative type, it's easily become a one of my favorites and is available on Netflix.  Another one of my favorite documentaries about design, also on Netflix, is Eames: The Architect & The Painter.

As a designer myself, I am constantly trying to figure out what makes a good design.   I think Dieter Rams, a well-known industrial designer, says it best in his ten principles for good design:

1. Good design is innovative
2. Good design makes a product useful
3. Good design is aesthetic
4. Good design makes a product understandable
5. Good design is unobtrusive
6. Good design is honest
7. Good design is long-lasting
8. Good design is thorough down to the last detail
9. Good design is environmentally-friendly
10. Good design is as little design as possible

Read more about Dieter Rams ten principles of design at Vitsoe.

It's interesting how lengthy and complex the process can be only to create something so simple in the end.  No matter how hard I try I can never get around the ten steps forward and nine steps back.  The only way I can ever decide if a design is good is if is functional, beautiful, and if I still like it ten years later.  Unfortunately, my answer takes some considerable time.
What do you think goes into creating a good design?