Hey, Mighty Spring CEO here: yes, we're making placements with the platform and new people are interviewing every week.
While we're still early-stage and in beta, our candidate and employer base is growing significantly on a weekly basis as well. As a marketplace, this is obviously key to driving more interviews/hires.
My impression is that it's fairly keyword-driven. You're told things like how you're 86% compatible for some job, and maybe you could bump that up to 88% by remembering that you have expertise in another couple technologies, etc.
I didn't end up closing a job through MightySpring, but I like their approach and wish them well.