With just a 17% stake, MS will influence the nook direction. It does create more value for shareholders as B&N is up 60% or more so far today. I do not believe that MS will be able to change the nook to a Windows 8 platform but a future nook with skype seems reasonable. A B&N book reader pre-loaded on all Windows platforms would be a great asset and potential revenue stream for B&N.
I was just thinking last week that it would be nice if the Nook had access to the Zune market. Right now the main markets for buying downloads are iTunes, PlayStation Network, Xbox/Zune, and Amazon, and Xbox/Zune is the one with the most obvious lack of interference between the goals of the two sides.