Google added a new quality to the sidebar: patents search. You no longer have to visit Google Patents to search the full text of the U.S. patent corpus since you can just click "patents" in the upright navigation menu. Here's an example.
It may seem like a minor development, but this shows that Google's particular search engines will be available from the sidebar. At some point, you'll no longer have to visit Gmail to find a contact, Google Docs to find a file or Android Market to find an Android app.