PowerShell Release Candidate 2 was just released and is available for download here.
If you’re using Beta 2 or any other build of Exchange Server 2007, don’t rush to install this just yet. Exchange Management Shell – Exchange Server 2007’s command-line management interface that’s built on top of Windows PowerShell – isn’t compatible with RC2 yet. (Beta 2 only works with RC0 – later builds not available publicly work with RC1).
By the time Exchange Server 2007 goes RTM, all these minor version compatiblity issues should be sorted out.