Google shows a large promotional message below the list of the search suggestions: "Love Google Instant? Make Google your Homepage." Since this feature is not yet available in your browser's search box or in Google Toolbar, it's a good opportunity for Google to promote its homepage.
Gary Price from ResourceShelf wonders if this is one of the larger promo ads ever seen in a drop down. I remember that Google displayed a similar message when Google Instant was launched: "Welcome to Google Instant. Feelings of euphoria and weightlessness are normal. Do not be alarmed."
I wouldn't be surprised to see that Google starts to show AdWords ads below the suggestions, a feature that has already been tested in Google Suggest.