Last year we had consolidated all our servers into a single data center. We were faced with a choice for setting up new DNS server. Our current DNS server (at the time) was RedHat Linux, but it did not belong to us. We used it at our previous "shared" space for DNS and email Relay. We had sufficient hardware for a new box - but we weren't altogether satisfied with the Redhat box. It seemed like we had to patch it quite frequently, and the features seemed like overkill for DNS and Email Relay. As a part of our migration we were fortunate to hire into an outstanding Cisco and networking consultant named Jeff Zimmerman (firstname.lastname@example.org). Jeff not only "fixes" our stuff but he "teaches us to fish". He's a great knowledge sharer and is very responsive. He recommended we switch to OpenBSD. His take was that it was designed with security and stability the top priority. He said it would run forever and we would never notice it.
After 3 months I'd have to say he was spot on in his assessment. The servers have not had any issues. We installed BIND, Sendmail and webmin. Webmin was for me - I hate telnet (ha). There are some gotchas. The install program was written by Koko the Gorilla (on a bad hair day). The configuration tools and interfaces aren't intuitive or sexy. In fact I'd say they are designed to be as "un-sexy" as possible. If you look in the dictionary under "unattractive" I think you would find "see OpenBSD". But besides being the pinnacle of geekdom, the OS works as advertised and does not require attention. In fact, I can safely say now that the biggest issue with OpenBSD is that it requires so little attention we run the risk of forgetting what we've learned about it.