just published on Virtualization Team Blog that Hyper-V RC1 is now available for download.

notice that current RC0 VMs with live snapshots are not able to upgrade to RC1. be sure to apply the snapshot, shutdown the VM and take a new offline snapshot in order to upgrade to RC1 without problems.

already done the upgrade on 2 of my servers and all my VMs are working without problems after applied new RC1 Integration Components on guest OSes.

FYI.