Earlier quoted context omitted.
Jessica Livingston posted her interview of Woz on the Founders at Work website. It's one of my favorite in the book because you really get a sense of the pure hacker/engineering genius Woz is. If you do not already own it, consider buying the book through edw519's link - it's an amazing trove. I bought my copy at Powell's Bookstore in Portland. http://www.foundersatwork.com/steve-wozniak.html
Thanks for the link, wallflower. I forgot about that. (Buy the book anyway. You just don't know which chapter might change your life.) This pretty much sums it up for me: "When you design with very few parts, everything is so clean and orderly you can understand it more deeply in your head, and that causes you to have fewer bugs. You live and sleep with every little detail of the product."
But then I saw your quote here, about the need to understand it, and the having very few parts makes that possible, by limiting the complexity.