You can choose to search for content located on either U.S. federal, state and local government websites or the entire Web
I did the obvious right away and searched for the Illinois 1040 form and the IRS 1040 form. Both searches came up with the PDF files right away. While the top search result was the same as a normal Google search, the following results differed slightly. If I restrict the normal Google search to only .gov sites, the results are closer, but still slightly different. They must be doing something additional to make the results more (or less relevant.
That’s all cool and everything, but the fun stuff is really on the main page, where there are nice little personalized blurbs for Whitehouse News, the Washington Post, the weather in DC, and a few other government news things.