10%! Whoa! That's insane. For the scale of projects I do as a freelancer, I'd be paying you about $3000-$5000 per project. Which is insanity for jobs board with an escrow service.
I think it all comes down to the client screening. If the service works as advertised and saves you significant time finding good clients, increases your rate because you have more worthwhile options to choose from and so can charge more, and/or gets you projects that are more interesting and fulfilling to work on, 10% is cheap. Tons of developers give up a much higher cut than that to work at agencies for those exact reasons.
That's great feedback. We are not really a jobs board...think of us like a recruiter who is technical and actually does their job right. Recruiters take upwards of 40% for project matches...that are pretty bad.(from what I've heard from talking to other freelancers)