I'm from the UK, so that may affect things. My experience is from around '08 to '11.
I was on Plenty of Fish, then OK Cupid. I found the latter far more pleasant, in both design and people. PoF is a mess, but I did find some interesting people on there. OKC seems to have gone downhill, presumably gearing toward smartphones and trying to compete with Tinder.
It really depends on what you're looking for. I'm very narrow and specific in who and what attracts me. I was sort of aware of this at the start, and way more so at the end. I went through profile after profile after profile, rejecting most of them as being of no interest to me. The ones that were of interest, I messaged. Some messaged me. I got a few dates, and one year long relationship out of them.
It can work, as long as you don't flip out if someone doesn't reply to you, and you don't go on a message spree out of desperation. Actually have something to say, and prepare to get profile fatigue.
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Of course, it's probably quite a bit more complicated than that.
You know sometimes, between the dames and the horses, I don't even know why I put my hat on.