Microsoft has released an interesting preview of WinFS StoreSpy v0.8 for the WinHEC 2004 Longhorn Build, ready to download and try.
WinFS Store Spy is an Explorer-like tool to browse WinFS. It offers flexible ways for you to quickly find your stuff and navigate the store. You can inspect Item, Relationship (all 3 types), Extension, Nested Element, and MultiSet properties.