Apple's Competitive Advantage

We're doing some research in class about any company's competitive advantage. We chose Apple and Im certain that there are people here who knows much about the company. I would like to acquire some information regarding its competitive advantage, SW-OT (internal strengths and weaknesses and external opportunities and threats), its major accomplishments and where it stands out in the computer industry.
Links to detailed articles or sites would also be nice.

Thanks.

-Don Ger-