Implementing the ribbon into Windows 7 and back-porting to Vista, is a great way to increase adoption rate but experiencing the not so graceful downgrade to windows classic, I am not sure how well it will be adopted by enterprise or server users.  Also how flexible will it become to customise the colours and styles of the ribbon for companies which at present style or custom draw their UIs.

It was nice to see an in depth look at how ribbons are formed, and good to hear the Fluent UI guidelines are being relaxed.