I’m not so sure about this — although it may be due more to the hardware side of their business: after the recent, disappointing iteration of their MacBook Pros I’ve heard a lot of people considering to switch (and actually switching).

Taken together with software quality issues, I wouldn’t be surprised if at least a subgroup of users are leaving Apple gradually. That subgroup being professional users, of course: Apple is still unassailed as a status symbol, and casual (+ mobile) users seem more than happy.