Lukas Mathis on the beginner-expert dichotomy:

The two goals — simplicity and depth — are at odds. Adding depth also adds complexity. So, what should you do? Go for depth, or go for simplicity?

To my knowledge, there is no conflict between simplicity and depth. There is only bad design. Regardless of the target audience and its level of expertise, feature depth should never be an excuse to design complex user interfaces. Jef Raskin explains in The Humane Interface (2000):

These sets of requirements are not in conflict; therefore, a well-designed and humane interface does not have to be split into beginner and expert subsystems. This is not to say that an interface must not be split on these lines. However, if you find yourself designing an interface and are tempted to provide "expert" shortcuts, consider whether you should instead redesign the existing method so that it satisfies the needs of all users with one mechanism.

While an ideal iMovie and Final Cut Pro merger is unlikely at the moment, Apple seems to be moving towards this direction more than ever before, despite the backlash.