Anecdotally, it doesn't appear to be any good for job searching. Lots of un-directed random messages from recruiters, but no real job sourcing.

It seems to be the fate of all socially oriented networking sites. They devolve into yet another advertising, spam delivery mechanism.

and then some flag is switched and I start getting 'a number of messages' from headhunters that (want to) waste my time. An easy way to be blacklisted by those spammers is to _always_ tell them "I ain't telling you my current $$$ or my $$$ expectations, the effing gig/role/contract has a budget+benefits, tell me what are those and I will respond". That will send those assholes away faster than garlic does a vampire. If they stay, then they mean business and they 'like' the CV enough to talk/negotiate with you.

There are some other 'smaller' ones (Indeed comes to mind) that still stick to 'find a job and nothing else'.