Hyper-V is now RTM and you should be able to find it on Microsoft Download Center shortly. This is a great release and the cornerstone for Microsoft's virtualization efforts. If you are wondering how VMM 2008 beta and Hyper-V will play together, read this blog post by Rakesh. http://blogs.technet.com/rakeshm/archive/2008/06/26/hyper-v-is-released-and-what-that-means-for-scvmm-beta.aspx

 The press release for Hyper-V is here http://www.microsoft.com/presspass/features/2008/jun08/06-26hyperv.mspx