One change is the navigation bar in the upper left corner. A similar one was already present in Google Docs and Gmail. Now they changed its appearance and put it also on their iGoogle site. This navigation bar makes it more easy to switch to other services which may be more appropriate to reach your wanted results (i.e. News search, group search, blog or video search,...).
As i mentioned before they also changed the way they place the results on the search page. This is the result of the launch of "Universal Search" which adds relevant video, image or code results to the normal web search results.
What all this will give, are most likely better search results, since Google will also start a "search for meaning" by translating the query in other languages and even do slight modifications on it to deliver better results.