FreeBSD 10, newly out, actually makes huge gains on OpenBSD's firewall, pf [1]. pf, by default, is not very thread-friendly, and uses a central mutex for packet processing. glebius has done some fantastic work that's unlikely to ever get ported back to OpenBSD's pf.
Now that FreeBSD 10 looks like it supports EC2 out of the box, I'm eager to toy with it again.
"As far as I see it: FreeBSD is the big one. Could replace Linux in pretty much any server situation. ZFS is amazing. OpenBSD is a bit more bare bones, but because of security might make a good router or firewall. What I've read about NetBSD is mostly research stuff. NetBSD is like a playground for OS researchers. (They have Lua in the kernel for example.)"
Now that FreeBSD 10 looks like it supports EC2 out of the box, I'm eager to toy with it again.
[1] http://lists.freebsd.org/pipermail/freebsd-pf/2012-June/0066...