Apple do one thing thats great and thats marketing, they have their market nailed down and unless they start to ship some kind of disease with their products, i suspect they will continue to sell like hot cakes.
Every mistake they make damages this though and id guess they really don't have much fuel left in the marketing tank.
Sheen? well i never really thought they had any after the initial iPhone, that was a really great device and certainly lead the market at the time, everything after that tho has been a steady down ward trend imo and as the general consumer gets more tech savvy their attempt to hide their hardware limitations will lead to large sales declines.