Though it's a couple days old, I just spotted Google's in-SERP Twitter integration yesterday... and now I am seeing it more and more.
In some instances, the integration is clean and adds clear value.for example, the Windows 7 search results are more powerful with Twitter because the web results are relatively static (meaning the content does not change frequently); therefore, Twitter results add new, dynamic content.
For search results that are more dynamic by definition - such as "Pittsburgh Steelers" - you will notice that the Twitter module adds to an already crowded and active page. I am not sure yet whether I think this is the future of search results or too much noise / pollution. Between images, news and ads - I visually lean to the latter but philosophically lean to the former.