Search box is among the cute features (apart from tabs, ad blocking, extensions, etc of course) which made me switch to Firefox. But do you know that is not required anymore?
You can put in your search text directly in your address bar. If the address bar does not contain a valid url, Firefox would consider it for searching. Here is an illustration:
Based on the result it will either take directly to the best match or show you the search results page.
All of the popular browsers (Opera, Chrome, IE) have this feature now.