Microsoft has quietly released a build of Windows Vista that is more recent than Release Candidate 1. The new build is numbered 5728, and comes with a number of caveats. The big caveat is this: the build is only available for a limited time, and will not be available via CD.
While this build is more recent than RC1, Microsoft says that it has not been thoroughly tested, and may in fact be less stable on some systems. Furthermore, the new build will not necessarily be upgradeable to the final release of Windows Vista, and may not fully integrate with Windows Update in the interim. Full details, including the download link, can be found here
Credit: ars technica