The advantage is that you can use single letters or words (“news”, “images”, etc.) to search Google’s other sites, and Wikipedia as well. This is simpler for some people than using the Google Toolbar application.
Search hits are shown using table markup, so screen reader users can move through the results quickly with table navigation commands. However, it currently only shows the top four results for any search.
The service is still in beta testing, but anyone interested can try out the Goosh interface.