I tried eHarmony once but it was virtually impossible to get paired with someone who weighed ~40lbs or more less than me (I'm 6'1" and 180lbs) so I ditched it.
Welcome to the singles thread...I've tried American Singles, Mate1, Yahoo! singles...many others. No luck.
Also tried eHarmony some time ago. Though I did meet some interesting women, I don't at all believe that there is any sort of 'scientific model' behind their matches.
I've done online dating a few times since about 1996. A few years ago it became more mainstream, but I kind of liked the earlier years when it was more of a 'geeky' thing. Got to meet some fascinating individuals. I like the way it allows one to meet people in a way that doesn't rely on the randomness of where one happens to work/live/shop/travel/socialize, but in response to issuing a 'query' for specific parameters.
I went on eHarmony. I was looking for a Godly woman first, so they only sent me matches that were like that. I got a lot of matches who would be a great partner for someone else. Fortunately for me, I finally met my wife. She is really a spectacular woman and I'm glad eHarmony opened up a network outside my church community. There are a lot of great Christian people who have trouble finding each other because we are busy and go to churches in different parts of town.