With the new features like; Reference, Bookmark and Diary, the new A9 (no more beta) is a very useful search engine.
With is focus on history, the Alexa data, the new references from Guru net, the bookmark and diary combine with the really smart idea to drag your all the links and title results, from any box (movie, history, reference, etc) to the search box or in your bookmark is making A9 a very good research tool !!!
PS: If A9 can add "site:" automatically when you drag a link to the search box it will be even more useful.