The BSD family, pt. 1: FreeBSD 9.1
I've been a big fan of FreeBSD since I first acquired 4.4 on 4 CDs. By that point, I had already spent a lot of time in Linux, but I was always put off by its instability and inconsistency. Once I had FreeBSD installed, it felt like a dream. Everything worked the way it was supposed to, and the consistency of its design meant even older documentation would be mostly applicable without having to figure out how my system was different. There is a reason why in the early days of the Internet, a huge portion of servers ran FreeBSD.
But, that was a while ago. Since then, Linux has matured greatly and has garnered a lot of momentum, becoming the dominant Unix platform. FreeBSD certainly hasn't stood still, however. The FreeBSD team has kept current with hardware support, new features, and a modern, performant design.