I have been on eharmony for three months earlier this year, received matches constanly, had three dates and met a man a fell in love with. He left me four months later and I am still trying to figure out why. Heartbroken I thought, let's try this again, and it seems either the culture or my expectations have completely changed: I get almost no matches. Weeks are passing with not a single match and the ones I have never respond. The matches are absolutely not what I am looking for: unattractive appearance, wrong age group, out of state, bearly able to spell any word correctly, none of my interests are their's, and their occupation is almost always "manager".
I wish I had the opportunity to exclude certain traits, hobbies, interests when creating my profile, or eharmony would evaluate why I closed a particular match.
Bottom line: don't expect too much, it is a huge coincidence if you find sombody you feel attracted to. There is no science behind the match making process except for comparing the occurence of certain search terms in two people's profiles. I also found out that most of my matches could be found on competing sites, so switching to another site won't change anything.