My department is thinking of doing personality screening of candidates. How much weight does your org put into them?

Management is thinking of doing personality testing pre-screen. I had a few questions:

1. On average, how many applicants fill these out if they're before first screen? Are we going to scare away good applicants at certain levels, or certain positions (Tech recruiting especially).
2. How much weight does your org put into them? Is any non ideal outcome a deal breaker?
3. Are there tests that seem to translate to good hires better than other tests?
4. Do you always eliminate anyone who doesn't do them, or still check on some candidates that don't (non referral).