I've round linkedin extremely useful recently for finding a new job after being made redundant. It's where the recruiters are, and where the jobs are posted, at least here in the UK. I even paid for a couple of months enhanced membership, or whatever they call it, as a career investment. I'd say its worth the money over the short-term.

As for maintaining an up-to-date profile, I think its worth dialing-down the access unless you're actively looking for a new job.

But the bs that people post to try to get "engagement" makes my head hurt. I'm about to start a new job in a few weeks and it'll be a relief not to have to bother with linkedin again for a few (hopefully many) years.