The CentOS development team is looking into another solution for the CentOS website and forums. But there is no real knowledge or experience about Drupal (especially for forums).
There's a lot to read and absorb on the new Drupal 6 but the good news is that if you've spent a while hacking version 5 you will need just a few days to get up to date.
With Drupal having won numerous awards and become the system of choice for many professional grade websites it's still surprising however that many new Social News (Digg Clone) projects choose to deploy the Pligg system in favor of Drigg for Drupa
I don't think much of Mollom on my Drupal site. It's not that I don't like it, actaully I freakin' LOVE it! It is just that I never, ever, have to think about it.