I got my first job out of college via SO Careers; it was a pretty solid gig, though I've moved on since then. I think I applied to several jobs through it, and wound up with a few phone screens leading to one actual interview in person. The response rate was pretty good; in fact, the only slow response I've had was when I applied for a job at Trello, but that was probably due to them being swamped more than anything else.