Much to learn from Steven Sinofsky's experience in going iPad full-time,many from the context that drove that change. Of particular interest to me was this paragraph:

A change-oriented mindset, especially for technology, is one where you force yourself to let go of the models you developed for how things work and learn new approaches. Re-wiring yourself and letting go of that muscle memory and those patterns that often took years to develop and perfect is incredibly difficult in a technical sense. It is also difficult emotionally. So much of our own sense of empowerment comes from mastery of the tools we use and so changing or replacing tools means we are no longer masters but back to being on equal footing with lots of people. No one likes resetting their station on the tech hierarchy.

This is something we talk about a lot as we shepherd design students towards the final stage of their Masters degree. There's a need to understand the territory that we're asserting mastery of, and to simultaneously recognise the significance of uncharted areas. The progression of proficiency, expertise, and mastery is complex and fractal, rather than linear and single-threaded.