In the last few days, Windows Management Framework 3.0 (WMF 3.0) has begun appearing in Microsoft Update (MU), Windows Update (WU), Windows Software Update Services (WSUS), and on Configuration Manager Software Update Points. This basically means that Microsoft is now suggesting that WMF 3.0 be installed on all of your servers where the update is applicable.
DON'T DO IT.
WMF 3.0 includes PowerShell 3.0.
PowerShell 3.0 is a great improvement to PowerShell. No question about it.
However, Exchange 2010 is NOT currently qualified to work with PowerShell 3.0. And, in fact, it doesn't. It will break. PowerShell 3.0 compatibility will come with Exchange 2010 Service Pack 3, due sometime in the first half of calendar year 2013 (word on the street says first quarter).
If you have installed WMF 3.0, you will also find that Exchange Update Rollups will fail to install.
Exchange 2007 is also not qualified to work with PowerShell 3.0. And, as far as I know, never will be.
You absolutely, positively, do not want to install the update on your Exchange servers.
You also do not want to install the update on workstations or utility servers where you have Exchange Management Tools installed.
I have also heard reports that SharePoint 2010 also has problems with the WMF 3.0 release. I can believe it. You should avoid that as well.
P.S. Exchange 2013 does work with WMF 3.0 and in fact, WMF 3.0 is required to install Exchange 2013. If you are one of the rare few running Exchange 2013, you do not need to be concerned about this.