Preflight or postflight, PitStop or FlightCheck? You should (and hopefully you are) doing both preflight and postflight! Here was a new thread over on PrintPlanet that my colleague Mark (and Charles) alerted us to:

Pitstop or Flightcheck?
We are a small print shop working with Macs, QuarkXPress & CS4 applications. We get some native files along with PDFs from customers for jobs, but mostly we get PDFs. Can you tell me the pros and cons to each of these software packages as a preflighting tool?
Source: http://printplanet.com/forums/prepress-workflow-discussion/18449-pitstop-flightcheck

Check out the full thread above, as there are some good replies. Watch FlightCheck Professional in action in this video demonstration, almost as good as a demo download FlightCheck itself!