I've been quite happy with the responses I get to Fedora/RHEL bugs in bugzilla.redhat.com, especially considering what I paid for it ($0). I also suspect that,

I've been quite happy with the responses I get to Fedora/RHEL bugs in bugzilla.redhat.com, especially considering what I paid for it ($0). I also suspect that, once a problem is identified as coming from upstream, the Red Hat folks get more attention from the upstream folks than others. Based on a small sample, Red Hat seems to do worse with "documentation bugs" - such as when their documentation described using raidtools in RHEL4, when it had been replaced by madm (which appeared to me at the time as "missing raidtools").