Anyone that has already decided to use Vista is unlikely to change their mind because of the Mac ads. IMHO someone considering an upgrade to Vista is much more likely to be influenced.
What does having glasses have to do with anything?
That is exactly the point Microsoft is trying to make. The Apple ads personify Windows as a glasses-wearing dork, while the Microsoft ads try to dispel that association.
I don't understand the new Microsoft PC adverts either. What does having glasses have to do with anything?