Here's another demo from the same reporting talk I presented sometime last year (video #1 available here).
This demo shows building TFS reports in Excel that go against the TFSWarehouse Cube. Excel 2007 had some great features that make building such reports a breeze. Advanced formatting/charting/pivoting capabilities, cubeset functions (not demoed) make Excel a very powerful BI tool.
Excel Services makes it very easy to share these reports with a wider audience. Data connection management, security, dashboards, KPIs make Excel Services a very powerful BI platform.
Here's the demo, hope you find it helpful.