SuperSite for Windows had an interview with Microsoft co-president Jim Allchin about Windows Vista.
Allchin thinks of Vista as being composed of three fundamental pieces, the core OS, experiences, and client core. "There is no part of Windows Vista that doesn't have some consequential improvement," Allchin told me, "whether it's the core level with IPv6, transactioning, or encryption, or any of the new experiences. Across the board, there are just reams of features. The question I keep getting is, 'well, yeah but, what's the big thing?' And..."