I've tried eharmony, match.com, and chemistry. I met one guy on eharmony (I wasn't matched with a lot) who was still in love with his ex that he had broken up with a WEEK before going to Eharmony (and looked nothing like his picture), I met a guy on match.com who was very cute, we were perfect for each other, dated for 8 months, and I swore up and down he was the one. Apparently, so did many other girls as I wasn't the only one he was spending time with, if you know what I mean

. Then I met a guy on Chemistry.com who seemed nice at first and he was 7 years older than I was at the time (He was 32, I was 25). Come to find out his longest relationship in his entire life had been 3 months and he didn't put a lot of importance on relationships, so I got out of that.
There's just as many dogs on online sites as in real life but online gives you more opportunity to meet guys you normally wouldn't have the chance to meet in real life. I know I never went anywhere (bars, clubs, etc.) to meet guys. I stopped "looking" and happened to meet my wonderful bf of two years in person!
My ex-boss met a girl on eharmony and married her 6 months later. That was a couple of years ago. They now have a baby and are having problems. Just don't rush anything. Online guys are just like real life guys. You have to get to know them, know how to spot the bad ones, and hope for the best!