I've had mixed results in the LA area, as an artist, as well as a band leader (short-lived band leader recruiting players).
I have never been contacted by another band. All of it's been on my side seeking out bands for keys or bass gigs.
From an artist standpoint:
What's good, is you can search by genre and by location, which I find helpful.
What's bad, is the bands that list every instrument needed (just in case) so you waste some time.
And your profile gives bands an immediate idea whether you would fit with them (good or bad, depending on your profile, I suppose).
Yes, it's expensive, and you sometimes send messages to folks that you never hear from again (again, if you do some detective work, you can find their website, etc) so you wonder if they ever get your message (or whether they are paid subscribers as well).
You still can find a stinker situation, or those habitual people that never seem to get a gig (you wonder why?) on any music meet-up.
Networking still probably a better overall approach.
From a bandleader standpoint:
I have had mixed experience finding folks for the band I started. You can find a lot of tire kickers or people that are in multiple projects.
I have heard from other band leaders that they find better luck with a higher quality person than with the free CL experience (lots of junk to get one good player).
And my current classic rock band uses it as a band marketing tool, since we're too cheap and too old to be able to set up our own website.
this has been my experience.