Ok, i got hooked on linux four years ago. Last year i switched to freebsd, and that is all that i run now (besides os x, but thats another story
). As other people have said, it is just like linux. In fact, if u have installed Slackware, you have more or less installed FreeBSD cuz they use almost identical installers. What i like about it is that, like Slack, it is BLAZING FAST!! It doesnt start all this needless shit like Redhat or mandrake does.
Also, it is SO MOTHERFUCKING EASY to install popular open source shit - you start the program /stand/sysinstall, you go to configure, packages, and then select ftp. There ya go, now you have THOUSANDS of packages, and all you need to do is select the ones you want, and it downloads and installs them. Oh yeah, and if you install linux binary compatibility you can run some linux programs on it.