Its a completely new backend they are using so ordering of results is different.

From searchengineland: "Based on the blog post, we can guess that this new infrastructure may include ways of crawling the web more comprehensively, determining reputation and authority (possibly beyond the link graph and what’s typically thought of as PageRank), and returning more relevant results more quickly, although Google’s Matt Cutts told me that the changes are primarily in how we index.Google’s new search is only infrastructure related and includes no UI changes."

http://searchengineland.com/caffeine-googles-new-search-inde...