Looked at FreeBSD, NetBSD and OpenBSD - NetBSD seemed to offer the most current packages (and ports) for my needs, OpenBSD had quite an attitude problem.
ZFS on FreeBSD (it seems to be supported on NetBSD, but I haven't found references of it being _used_ in the wild) is a decent reason to give that one a chance again.
One example that I came up with again now:
prosody is on 0.8.2 in FreeBSD [1] and 0.9.1 in NetBSD [2]
Nothing critical, not to hit on FreeBSD here, but checking a couple of (weird?) packages I'm interested in NetBSD was always equal or ahead.
1: http://www.freebsd.org/cgi/ports.cgi?query=prosody&stype=all
Also, the website is quite sparse and I couldn't find out if they use the same ports tree as OpenBSD. The latter is (see my comment in the same thread here) out of date for a couple of packages I'm interested in. Just like FreeBSD's.