I do "use" LinkedIn to get queries regarding opportunities and to keep in touch, but I'm not a frequent user.
However my most interesting recent usage of LinkedIn was signing up to pay for Inmail in order to be able to message a few high level executives at DHL to complain when a delivery was stuck in limbo. One day later and two Senior VPs (out of 3 I messaged) in different offices had told their staff to sort it and I was Cc:'d on a flurry of message exchanges that started or ended with pointing out that "SVP so-and-so wants to be kept in the loop".
Two days later the package that DHL for a month had told me they didn't have (and had told the sender was on it's way back to them), and couldn't have corrected the delivery address on even they did have it (it was accidentally - my own fault - sent to our old office) turned out to be sitting in a depot 5 minutes away, and was promptly delivered (to our new office).
That to me highlights a benefit of LinkedIn: Everyone can get access to relatively high level people, in part because the barrier to hassling them is high enough that it's not massively abused: If you're not in their immediate network you can contact them directly only if you've paid, and only quite few at the time. While it's annoying to have to pay, it's better than not being able to reach these people on occasion.
I'm going to consider using InMail that way whenever someone annoys me enough to be worth the cost of another month of InMail subscription from now on given how well it worked with my DHL problem.