Through backwards compatibility, Vista will not be an optional upgrade, and it won't be a pleasant one for those affected by DRM.
Once it starts hitting the mass market (So when PC giants start selling it preinstalled instead of Windows XP) people will just accept it, as most do with all Microsoft products (Can you say "Internet Explorer"?), and they will do this because that is what Microsoft and other "trustworthy" sources tell them is best.
Microsoft will oviously only tell people about the benefits, such as security and the eye-candy and leave out the drawbacks of DRM and backdoors since their role, and all of Microsoft's customers who sell MS products will be to promote them, since they are faceless corporations, driven by money.
Depending on how good or bad Vista is, I may be tempted to switch to a Mac. I'm willing to bet other people are also having similar feelings. However, the average Joe public will not make the change since Windows is all they know, and can't stand getting to know a whole new OS, or don't know how to install Linux.
By the way, this is coming from someone who, up until a few weeks ago, was a gamer (4+ hours/day).