[Athas]

I use OpenBSD on my personal server. It does not do anything advanced, but runs email, a few websites, IRC bots, and such. I am not a professional systems administrator, nor do I consider myself a particularly competent one (I'm a compiler researcher). OpenBSD is the only system where I feel confident that what I have set up will be reasonably functional and secure. This is partly because OpenBSD comes with sane defaults and excellent documentation, but also because most software in the base system has fairly few features, and is focused on the common case, so I have less rope with which to hang myself. At the same time, it is so simple that I can actually understand in detail what's going on, and what the configuration files do.

Experienced systems administrators may have other reasons for preferring OpenBSD - I really wouldn't know. To me, OpenBSD certainly fills a niche for someone who is fundamentally knowledgeable about computers (and willing to read documentation and write configuration files), yet is not a full-time sysadmin.