Edit: Answers to the title question have now shown up, and so the post below is now superseded by this one.
In most respects — including most data warehousing respects — Oracle’s query optimizer is the most sophisticated on the planet (even ahead of IBM’s, I’d say). But in all the Exadata discussion — and also in a good, comprehensive review of Oracle’s data warehouse technology — I haven’t seen any claims that Oracle has tackled the hard problems of parallel analytics.
Yes, Oracle is now getting data off of multiple disks onto multiple processors at once, without SAN bottlenecks, and doing some local filtering. That’s the heart of the Exadata storage story, and it’s indeed a huge advance over Oracle’s prior technology. But what happens to the data after that? It’s sent over to a RAC cluster. And unless I’m terribly mistaken, any further processing will be done on just a single node in that cluster.