RHL 5.1 was my entrance to Red Hat. It stunk. RHL 7 was my first RHL that I could use and enjoy. I was using slackware previous to that. Nowadays, as long as the system is desinged sanely, it usually doesnt do more than bug me. Like SuSE. Linspire, Ubuntu, CentOS and Fedora are all just forks as to how I want to do things.
For uber-reliable systems, CentOS is a nobrainer. If I dont need gaming or windows interoperability, OpenBSD is the choice then (for the uber systems at least).