Those saying they see little use for LinkedIn or that it's worthless likely don't have great paying jobs or work in a very professional environment. For those of us that do, it's a very important tool.
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Anyone making over $60k/yr and not making use of LinkedIn is missing out on the chance for a much better paying job and being generally better at your job (those making less than that too but it tends to be even better the higher up you are).
What you have is a narrow view of "paying jobs" and "professional environment." I'm uni faculty--not the worst gig available--and LinkedIn offers relatively little return on my investment. I won't cry about Apple integrating it more completely, but it's by no means a key component of my profession.