Five years ago, I decided it was time to get back into the corporate world. I've had a LinkedIn account since Day 1, so I posted a status update saying something like, "Guess it's time to dust off the resume and dip my toes back into the corporate pond." I didn't think anything of it.
Five minutes later, I got an email from an ex-coworker (back in the 1980s). He asked if I was really looking for a corporate job. These days, he is the President of a multi-million dollar company. Seems this person had been keeping an eye on my career and successes over the years, and, in his words, didn't want to miss out on the chance to hire me.
Long story short, we got together two days later, and I had a new job. A very, VERY good job!
So yeah, I love LinkedIn. And I use it all the time as part of my job. I'm not crazy about the "endorsements", but the good news is that you can "Manage Endorsements", and hide any that you care to hide. They're still there, but no one can see them.
The recommendations, on the other hand, are awesome! I get 'headhunted' regularly, and I'm sure my excellent recommendations (and I have quite a few) from legitimate folks (company owners, VPs, vendors and association contacts, etc.) are, in part, the reason for this.
Also, LinkedIn Groups are another valuable area, IMO. Both from a networking and marketing perspective.
At the end of the day, LinkedIn is what it is. It's more valuable/useful for some people than for others. I will say this: When we're checking out a potential hire, LinkedIn is one of our sources for info. If you're out there, then keep your profile up to date. And don't treat it like Facebook: Use a photo of yourself, not your dog. And for the love of GOD, do NOT badmouth your employer via snotty comments and such.