The previous release candidate was available only to around 15,000 beta testers out in the wild, but with the release of the SP1 RC Refresh, it seems to have been opened up to the general public (ie. you, the random punter), to download and install.

There is a warning not to use this release on any primary or mission critical machines, so pick your test box carefully.

I, being one of those daredevil types, may well back my primary laptop up and give it a go sometime this week and report back. I mean, if I'm going to test it, I may as well test it in anger right? I'll be the guinnea pig, and you can all learn from my (potentially doomed?) example. :-P

Be sure to read the instructions at the download site thoroughly before trying this at home kids.  Download details: Windows Vista Service Pack 1 RC Public Availability Program