A small page. A small page is quick to download and generally faster for your browser to display. This results in a minimalist design aesthetic; extra fanciness in the interface slows down the page without giving you much benefit.
Complex algorithms with a simple presentation. Many search features require a great deal of algorithmic complexity and a vast amount of data analysis to make them work well. The trick is to hide all that complexity behind a clean, intuitive user interface. Spelling correction, snippets, sitelinks and query refinements are examples of features that require sophisticated algorithms and are constantly improving. From the user’s point of view search, almost invisibly, just works better.
Features that work everywhere. Features must be designed such that the algorithms and presentation can be adapted to work in all languages and countries. Consider the problem of spell correction in Chinese, where user queries are often not broken up into words or Hebrew/Arabic, where text is written right to left (interestingly, this is believed to be an example of first-mover disadvantage — when chiseling on stone, it is easier to hold the hammer in your right hand!).
Data driven decisions - experiment, experiment, experiment. We try to verify that we’ve done the right thing by running experiments. Designs that may seem promising may end up testing poorly.