Well, a surface is explicitly designed for the lowest common denominator. Context-sensitive menu options that change what they do have always been a bad thing as they completely block development of muscle memory for actions; they would only ever logically be useful for people who are not fully able to remember multiple locations and associate them with different actions.
"Make a completely foolproof product and only a fool will use it".
> Context-sensitive menu options that change what they do
The whole point of a context-sensitive menu is that it changes depending on your context. I think they're usually for advanced users -- often the right click menu just duplicates commands from the global menu but it's a faster access method. The Win8 case requires it for all users.
Of course if the context is the same, then the menu should be the same. (Maybe that was your point?)
"Make a completely foolproof product and only a fool will use it".