Ask HN: Employers -- How has StackOverflow Careers performed?

As an employer/manager looking for engineers and other stack-related candidates,

- How has your luck been at finding/hiring candidates via StackOverflow Careers?

- What quality (1-10 scale, 10 being amazing-est) were your candidates?

- What role(s) did you post for?

- Have you hired anyone? What role(s)?