I think the RPM distributions are best, seem to have little to no problems and having ART support is great (take this opportunity to say thanks scott btw) so I would say RHEL/Fedora/CentOS .. I currently use Fedora 2 and while there are no problems and you can keep security upto date using legacy etc in the future I would go between RHEL and CentOS, since I don't need to pay for support I would choose CentOS.