Google Caffeine is a "buzzy" thing but most people do not know what it means to them.
From a content and SEO purpose it has to do with how content is stored on the web. Now that Google has crawled a page, Google can push the page through the index much more quickly. It instantly pushes the page through.
It does not change how often they crawl pages. It just means that a minute after they crawl is that it will be indexed.
The other thing that has changed is that they have the capacity to store any type of data in the future. So this way, Google doesn't have to build out a new infrastructure, they can just make a few changes.
Many people think this is an index change and impacts ranking. But it really is not a ranking change.
This indexing speed has been a goal of Google and it makes sense as the website gets larger. At some point, if Google used the old infrastructure, they would have been bogged down and unable to keep a fresh index.