Google latest rule is that they will consider tweets to make real time results more specific. Better to concentrate on twitter.
Whatever the new rules may be, I haven't seen any change to clients sites where they hold top positions because of: Unique, good content Proper construction of page (title, description, h1 tags) Good reputation across the web (incoming links)
In short, Caffeine: allows Google to crawl and index more pages allows Google to crawl and index pages faster.
what ever mattcutts speaking om his blog or any conference you can take it seriously as Google Specking. He talked about Google caffeine and it was fact