A lot of people have answered that it is a useful tool for job searching. My experience was a bit on the other side of the coin. Our company wanted more of a presence on the site to gain visibility so managers like myself were encourged (told) to sign up and post on it. We also received video training on how to write catchy descriptions of ourselves (under 50 words ofc) and stuff like that.
The site is just a circle jerk. I hate it.
From the online job searcher's point of view, it's one of the least awful circle jerks in a Dante's Inferno-esque series of circle jerks. It is only the first or second circle jerk, at worst.