I am planning a project called Fpcp (Full Page Caching Preparer) to improve Magento performance. Yeah, it is called Fpcp and very similar to another module Cpfp (Cms Page Foot Print).
I have a bit research on Magento Enterprise only features, and pick full page caching as my next interested project. I do not know how Magento Enterprise implements full page caching, but my idea is rewriting all blocks containing session related content with an ajax get method.
I tested full page caching can offer 50% performance improvement. It’s not massive improvement, but worth having.