I know this isn't ideal, but typically how compatible are Centos5 rpms with RHEL5? Is the only real difference the enterprise package management, or are the two OS as divergent as Fedora and RHEL?
The CentOS site says it best (emphasis mine):
CentOS is an Enterprise-class Linux Distribution derived from sources freely provided to the public by a prominent North American Enterprise Linux vendor. CentOS conforms fully with the upstream vendors redistribution policy and aims to be 100% binary compatible. (CentOS mainly changes packages to remove upstream vendor branding and artwork.) CentOS is free.