Donald Farmer from Microsoft speaks to Stephen Swoyer at TDWI about Microsoft's Project Gemini.  More details emerge of Gemini.  Apparently Donald says that any ad hoc business intelligence clients like Tableau or Business Objects can connect to the Gemini cubes.  This would be very interesting because you can extend beyond Excel!  I am assuming that you would query these cubes using MDX and would connect via either ODBO or XMLA.