Yeah, I've used it before. Met a lot of really great people actually. With a lot of questions answered, their matching algorithms can be pretty handy. If you find someone with a 95% compatibility rating, even if you don't have 'the spark' with them, chances are really good that you will at least get along well and be able to have good conversation and stuff. And looking through the questions at how someone answers stuff can give you a lot more understanding about them as a person and how they think than the profile. People always put on a 'best case' face when they write up a profile. But as they answer the questions, their real personalities often start coming out.
It also depends a bit on your personality, what you're looking for, and how... unique your needs are.
Women enjoy more engagement than men, but get addicted to the positive attention and end up squandering the genuine opportunities that come knocking.
Men see windows of opportunities everywhere, everywhere! So many girls with hot fappable pics! What they fail to see are the other men fapping away to the same girl, but they have six packs and/or money to burn.
Rarely does something good come out of online dating. To say otherswise is akin to saying good things come out of playing the lottery, I mean look at all of those winners!