I just deleted my LinkedIn account. I obtained zero of my last few jobs from using LinkedIn (at least primarily), and I got 'recruiters' contacting me for initial screens that led nowhere, I think because they don't really know how to filter down to what their client needs very well.
I would compulsively check my account however, and felt the need to respond to all kinds of messages I got on there in some form or fashion. When I took an honest look at the time I put into using it and what I actually got out of it, it was clear for me it was a time sink with no reward other than 'feeling like I'm doing something to help my career' when I could have spent all that time actually doing something that mattered to me.
Edit: If a company won't hire me due to not having a LinkedIn account, I guess that's a downside, however I don't see how a profile there is much better information than a resume I've prepared.