IHers who run job boards - tips, advice, suggestions?

I have an idea for a new twist on a job board. I know a few IHers here run job boards. I'm curious what you've learned running a job board so far. What are the challenges? I'd think getting employers is the easy part, but raising awareness among applicants about your job board is the hard part. Did you just brute force past the early chicken-and-egg problem? Who's more receptive on the employer end for sales - hiring managers, recruiters, or HR?

I think there's enough room for one more. What advice would you have if you were starting out launching a new job board today?