An evening with Google's product manager - Marissa Mayer:

• The prime reason the Google home page is so bare is due to the fact that the founders didn't know HTML and just wanted a quick interface. Infact it was noted that the submit button was a long time coming and hitting the RETURN key was the only way to burst Google into life.
• One of the biggest leap in search usage came about when they introduced their much improved spell checker giving birth to the "Did you mean..." feature. This instantly doubled their traffic.
• Google has the largest network of translators in the world.
• The infamous "I feel lucky" is nearly never used. However, in trials it was found that removing it would somehow reduce the Google experience. Users wanted it kept. It was a comfort button.
• Gmail was used internally for nearly 2years prior to launch to the public. They discovered there was approximately 6 types of email users, and Gmail has been designed to accommodate these 6.