Awful. I spent two years on that site, met 2 people in person, sent literally 100s upon 100s of messages. Giant waste of time - I'm thoroughly convinced online dating does not work. Have you seen the movie Catfish? Its kind of like that, no one is who they appear to be on the internet. Sorry if I'm ranting. OKCupid is "free", but it took away many, many hours that I'll never get back.
I met a girl one time who said "You get a good relationship when you need it the least." I think that is the crux of why it doesn't work or can't work. It's like when you find something you've lost, but only after you stop searching for it.