Interesting, in my experience 2K will give you really good uptime, not quite as good as a linux box. If you patch all the time it helps because thats usually a reboot..
Interesting, microsoft.com has longer uptime than redhat.com, as of today.
33 days:
http://toolbar.netcraft.com/site_report?url=http://www.redhat.com
56 days:
http://toolbar.netcraft.com/site_report?url=http://www.microsoft.com
Gee, that's almost twice as long, isn't it?