Seem a smaller database than they talk about, but very good to manage about over optimize and SE spammer sites and very nice results with clean little sites and fair to good results for small-middle (200 - 1k pages) but poorer to big one, and also to governement web sites. The clustering is far from Clusty and the Web site location is just average like all other services (and very hard with the technology to be better for now).
But it is still in beta and really giving very good effective results within the really small delay they got to put that up (and differents from all the other "new" sources) and very good new tools and options to dig deeper with a not so bad user interface (should take a bit more minimalist view here). And with all the good and many advanced search features not seen anywhere else, you should keep a eye on it.
Hope for Google, Exalead will not merge, fusion or make a deal with Vivisimo, because if they can handle a better clustering, fusion databases or crawl them deeper with a little tweak in algo for the biggest sites, the Goog will fall under the hundred soon ;-)