As RHEL/CentOS users are used to the RHEL update style I'd say updating EPEL
packages in RHEL style is the safest bet.
What is the RHEL style now? They have 5.1.x and 5.2. 5.2 has new
features, 5.1.x keeps the same ABI. If RH can't decide, we're going
to have difficulties also.
Keep in mind that Centos isn't doing the 5.1.x AFAIK, but still, RHEL