Launched at the start of December 2008 apparently.
I'm not clear as to how the Hyper-V protection will work though - Will we have to pause Hyper-V guests or not during protection?

More details here:
http://blogs.technet.com/jbuff/archive/2008/11/24/what-is-new-for-protecting-sharepoint-with-dpm-2007-sp1-technet-edge-video.aspx

http://cs.thefoleyhouse.co.uk/blogs/karl/archive/2008/11/29/dpm-2007-sp1-real-soon.aspx