I think I managed to get more or less 30 dates from online dating in my life. I'm 24 and have been doing it since I was 17. I took a break from it in 2010 (when my hair really started to go down the drain) and in 2012 (when I had my man boobs on top of the hair loss).
Everything I've read here is accurate, except for the desperation, at least for the women, because pretty much all of them are on dating websites now (Facebook counts as one).
So you can say 99% of girls are desperate. You'll find all kinds of girls. I managed to pull girls from 5 to 9 in the looks range.
We cannot say the same for guys, as they'll often use online dating as a substitute because they can't approach girls in real life.
It's all based on your main profile picture, you can write anything you want on your profile, it just won't matter. Some girls will take the time to read your profile, but they're the exceptions.
I see it even more clearly now with Tinder. Even though I'm good looking and have been offered modelling jobs, I'm still not one of these "demi-god" they are looking for.
If I send 25 messages on Okcupid, I'll get 1 reply. I just say "Hey, how are you?", and it usually works. It also proves the fact that it's all about the picture profile, if she finds you attractive, she'll reply.
My stats are quite low, but I'm honest about how I look: no hats, no combovers, I'm just bald on my main profile picture. I guess it must affect my reply rate. I'll see if it changes after my transplanted hairs grow. You can't say the same about the girls regarding honesty. A lot of them are SIF (secret internet fatties) who will use creative angles.
Only one approach works for men on those websites: upload a very good picture of yourself, possibly taken by a professional, spam message girls as much as you can, copy/paste is your friend. After not more than 3 lines of discussion, ask for her number/Skype/Facebook, talk a little with her some more, then ask her to meet. You should be doing that fast, do not wait more than 2 days to move the interaction forward, because you will have a lot of competition.