I've used it both ways, both to find a ride with someone else and to find passengers. It's worked pretty good so far...I like being able to carpool without having to necessarily do it twice with the same passenger, and just pay for gas and tolls instead.
Set up a weekly carpool and it's worked great so far. Found two people who live near me and we get along well, no problems so far. Cool to be able to see how much CO2 I'm saving every week.
Found a great passenger for a ride last summer! Really glad I used you guys, it would have been waaaay to expensive to make that trip on my own! Great! ;)