I have just completed installation of Windows XP SP2 RC2.
I upgraded from RC1 very smoothly via the Windows Update Site. If you have RC1 installed and you go to the Windows update site and do a scan it will pick up that RC2 is available. Once downloaded it went pretty quick. A reboot at the end ... and i am up and running on RC2. It seems like a very solid build and so far i would recommend it to anyone. Some have commented that i should have uninstalled RC1 first ... but that was after i had done it... and it seems i didnt need to anyway.