I think Power BI may be the coolest feature of an already impressive Office 365 cloud offering from Microsoft. Power BI's ability to combine views and queries from disparate data sources into visual reporting is a slam dunk, but innovations like "Q and A", which allows users to mine their data with plain English questions, is super innovating and a very clever way to give users business insights.
With Cortana Analytics, announced earlier today, Microsoft is extending the plain English ways which users can use their data. Power BI + Cortana looks like an impressive new opportunity to leverage the explosion in data combined with over increasing preference mobile interfaces.