Microsoft is planning on delivereing a new beta drop on June 20th, so beta testers will be seeing this very soon. If you are NOT currently a beta tester: Go to http://beta.microsoft.com and sign in with a Microsoft passport. Then logon to the site using the guest ID: mshPDC, select Microsoft Command Shell and select/complete the Survey in the left column. Access to the beta should be granted within 48 hours.
Jeffery noted, and it was explicitly NOT under NDA, that Monad-MSH will ship as part of Exchange 12 (in 2006), as well as WinFX. There's also the distinct possibility that it'll get into Longhorn client, although that is not yet confirmed.