Vista has had quite a bit of bad press. Between past XP experiences during its early releases, Apple ads and word of mouth, most people have a bad impression of Vista. Microsoft set out to study this with the Mohave Experiment. The study discovered or at least made the claim that people's negative impression of Vista is purely from word of mouth and that if they actually gave it a chance, they would love. The usability test video makes a good case even if it is a very superficial test.
Skipping the validity of the tests shown, it is an interesting study of how bad of an influence word of mouth can have. Microsoft already has a rough time maintaining and cleaning up their brand and their market doesn't help the matter. Enterprise level system admins are many times the first to review these new OS's and will also be the first to say no when a potential disturbance presents itself. The opinion of system admins or family admins goes a long way.