This guy is expected to concentrate on Blackomb, not Longhorn/Vista.
I expect there will be "significant" defections from the Windows development group since this guy's management style is quite different from what they have experienced in the past.
Since Microsoft's documentation is practically non-existant, if they lose enough programmers Blackomb will be another "from the ground up" project like Longhorn was supposed to be. Expect deadlines to not be met.