...but I did just get a new version of Windows Update v5.
It looks to me as though MS is going to push SP2 through Automatic Updates. I'm not sure this is a good idea. Yes, everyone should have SP2 - but only under their control, and only when they ask for it. This isn't a small patch - the RC2 download was 200MB or so. Even though Windows Installer 3.0 allegedly supports differential binary patching, if everything has been recompiled with the latest /GS implementation, a heck of a lot will have changed.
I just hope I won't have to uninstall RC2 before installing the RTM version.