Me, in WinInfo:

For Windows Vista SP1, the RC1 release brings no major changes, but does include a number of feedback-related enhancements. For example, SP1 RC1 requires far less free disk space during installation, and provides more guidance about the update earlier in the installation process. Microsoft is shipping SP1 RC1 to testers today, and to MSDN and TechNet subscribers on Thursday. Next week, the company will make the release available to the public via a Web download or, optionally, Windows Update.

Obviously, I'll be writing up something for the SuperSite later in the week.