I am a small company that was needing to hire a service manager. I placed the ad on a Wednesday and promoted it with a budget of about $75 per day. My ad was fairly specific (Pool Service Manager) in its requirements and of the responses I got, about 25% were plausible candidates. I paid about 30 cents an impression I think on average. The site must be pretty dead on the weekdays, cause my spend was in the single digits, but went to the budget on Friday, Saturday, and Sunday.
Overall, this was my first foray into an organized board. We'd used Craigslist before but it's such a disorganized zoo. I thought about Monster but it was more expensive and this got us viable candidates at lower cost.
One final thing I liked was the ability to have the candidate answer up to 3 questions when submitting online. We used these for quick screening questions.