I intstalled OpenBSD for the first time last week. I'm setting up a Nessus scanning machine on a 500MHz P3 that has seen better days. So far I'm impressed with OpenBSD. It's lightweight and responsive. Its simplicity is impressive. It has everything it needs without getting too fancy. Its hard for me not to like a default install (sans X-windows) that only has 15 processes running. After I get everything working the way that I want it, I'll kick the security level up. Yeah, so BSD provides a means to prevent configuration files from changing while its running. Oh, how sexy! Also, the effort the OpenBSD team has put into code auditing is beneficial to the end product. Only one remotely exploitable flaw in the OS in the past two years. No one else even comes close.
I've been running our proxy server off of SuSE Linux, but if all goes well, I will likely migrate this to OpenBSD also. I've got a bit of work to do in understanding the PF firewall, but my initial impression of PF is that it is quite natural.
