System Center 2012 R2 Preview is now available for download through the TechNet Evaluation Center. This is a VERY large download so be prepared to wait a while for it to complete. This download is for pre-built virtual machines that you will need to install to a local Hyper-V Host. If you would like to install the bits directly to Windows Servers in a lab environment, see the download link at the end of the blog post.
System Center 2012 R2 Preview
If you would like to install the System Center 2012 R2 Bits directly to a Windows Server and configure to your test environment, this will require for you to have a TechNet or MSN subscription to download the individual installers from the TechNet site - installers.