I pretty much left my programming job to come to HS. As i'm in the current batch, i'm entering the nob market around now. While I don't know about average salary or job placement rates, if you are a professional programmer before hacker school you'll only be a much better professional programmer after hacker school, and that means it won't be too difficult to get a job.

But Hacker School is not a job placement program. It is a place for people who love programming to come to become better at their craft. That this results in increase job opportunities afterwards is often a beneficial side effect, but not the primary motivator for people to come here.