Very interesting read at http://blogs.msdn.com/e7/archive/2008/10/15/engineering-7-a-view-from-the-bottom.aspx, where Larry Osterman describes some of the differences between the Vista project and the Windows 7 project.
A part that made me chuckle, was: "This is where one of the big differences between Vista and Windows 7 occurs: In Windows 7, the feature crew is responsible for the entire feature. The crew together works on the design, the program manager(s) then writes down the functional specification, the developer(s) write the design specification and the tester(s) write the test specification. The feature crew collaborates together on the threat model and other random documents. Unlike Windows Vista where senior management continually gave “input” to the feature crew, for Windows 7, management has pretty much kept their hands off of the development process."
What I find most interesting is how the article ends - where the choice of words indicate that Windows 7 already is feature complete.