Well i have been messing with FreeBSD 4.5 kernel and the power is unlimited. Was having a rootwars with some friends and found that their are a couple things you can do to get root, if you have an account on the box.
However OpenBSD is still my choise for "best" os. I mean you can pretty much compile anything to run on it. And if you are running linux binary support you can run all linux stuff too.
My buddy wrote this how to:
http://www.bsdtoday.com/resources/HO...emulation.html