As a member of the Exchange Server support team nothing gives me more pleasure than announcing this 

" We always talk about listening to customers and sometimes this is written off by many as 'marketing speak'.

In fact, we do take feedback seriously and no input is more important to our engineering processes than your voice. Earlier this year we made a decision in one direction, and due to the feedback we have received on this blog and elsewhere, we have reconsidered.

In the coming calendar year we will issue an update for Exchange 2007 enabling full support of Windows Server 2008 R2.

We heard from many customers that this was important for streamlining their operations and reducing administrative challenges, so we have changed course and will add R2 support. We are still working through the specifics and will let you know once we have more to share on the timing of this update.

So, keep the feedback coming. We are listening. "

The main idea is " We listen the voice of the customer " 

Source :

You Had Me At EHLO... : Supporting Exchange 2007 on Windows Server 2008 R2
http://msexchangeteam.com/archive/2009/11/04/453026.aspx