I've used it before. I'd say its best feature is the "Ports" system (from which Gentoo's Portage was not surprisingly based) which allows you to easily install software from source from a huge repository. I'd say it's much easier to install than Gentoo, but it is definitely *not* for anyone who's afraid of the command line. In fact, many people don't even install XFree86 with FreeBSD.
And plus it's got that adorable mascot, Beastie the FreeBSD Daemon