Its funny you know, UAC (those annoying pop ups) which is one of the most maligned features of Vista is one of the best steps it made. UAC goes someway to bringing Windows up to the security level of OSX/Linux, running users at the lowest level of priviledge necessary.
However, Vista is awful, I don't have sufficient technical knowledge to say where it went wrong, but XP works great and just suffers from its age. Windows 7 runs great with all the new features and accompanying resource demands as befits its age. Vista, well Vista just doesn't run well, its sluggish, unintuitive without the great aero features of 7 and really is just no better (or at least very little better) than XP.