This is my first time seeing Twitter results integrated within a Google search results page. The below query is for "Windows 7" and you will notice a dynamic Twitter 'widget' in-line with other results. The unit scrolls automatically through the most current Twitter results for that query.
Like the recent Chrome Extensions, this is lightweight, minimalist and is visually very clean... in fact, it is so clean and flush within the standard search results, that it is almost confusing. The widget's animation is what visually separated the Twitter results from the web results.
When you click see all results, you arrive at a full-page Twitter search results page. It looks and behaves similarly to the in-page unit - though it is cleaner and includes Twitter user-icons.