I upgraded my demo machines from beta to Release Candidate of Hyper-V last night, and I'll be using them for my Win2008 demos at the Auckland Launchwave 2008 event next week.
This morning it was great to wakeup to the news that we have announced the Hyper-V Release Candidate!
The Release Candidate 0 (RC0) update to the Hyper-V role provides improvements to security, stability, performance, user experience, forward compatibility of configurations, and the programming model. All users of the Hyper-V role are encouraged to apply this upgrade
The download is here, the page also includes installation and migration information.
More info on the Windows Virtualisation Team Blog