Windows 2003 SP1 has been released and is available via Windows update.
I installed on my live server and all was well. I even managed to get the new firewall up and running (always scary using remote desktop). Just make sure you use the new security wizard before starting it otherwise it blocks all ports by default (and chucks you out of remote desktop)
I finally took the plunge earlier today. The install went fine on two servers and took a lot longer on a third server running Sql Server. It took about an hour and a half to install and required two reboots.
I was bricking it when I couldn't get back in via remote desktop the first time after reboot but got in the second. Whew.