Good post, I think that artist’s activity is more about imagination and skills of showing it. Design consists of solving problems using particular set of tools considering different kind of constraints.
Artists don’t have restrictions, they absolutely free to use any kind of technique to express their idea. If we talk about Apple it’s not only about creativity but hard work of defining environment for user and appropriate dialogue through interface with a person.
There are a lot of methods of generating ideas, the main point of them there must be constant practice, because in the beginning it’s harder to come up with great idea.