Secure OS

Nowadays, probably the most secure OS are hardened Linux systems (like hardened gentoo and RHEL), Trustes Solaris 11, OpenBSD, QubesOS, Novell NetWare and OpenVMS.
What do you thing is doing the best security approach of this OS.
And what do you thing is better in practise?
(You can also include other OS you consider secure)
And what do you think os security on microkernel systems?

I install the service packs as soon as Microsoft puts them out.
Don't use third-party browsers such as Mozilla Firefox.
Windows Vista has proper refined security controls.
I don't know, Windows is hybrid and it's the most secure OS out there.