Over the years I've used all 3 of FreeBSD, NetBSD, and OpenBSD for various duties, and found all to be clean and sensible.
And dare I say, enjoyable to use. I'll freely admit they may not be for the uninitiated, but if you grew up around the 90's era "Unix wars" you'll probably be comfortable enough with any of the BSD.
Added bonus that some of that same old Unix iron will run some of the BSD as well, if you've still got the gear knocking around the basement or garage.
In any case, cheers to Colin for sharing the results of his FreeBSD work!