I've looked at them but wouldn't sign up to one. I just think if its all too obvious, its gonna be rushed or forced. Better in my view to join social groups that get you to see more people of the opposite sex, so much better if you can like someone and then something develops from there I recon.
I think its also good to not need someone in your life, but should they come along then they can enhance it. More and more people are going the single route these days, maybe relationships (romantic) are on there way out? I do find it odd that we have this in built desire to be with someone and yet it can be awfully difficult to do anything about it, and yet you see couple's all the time, so some are able to do the dating game alright.
CS 101