If you thought licensing for OCS 2007 R2 was complicated we now have the licensing for Lync. http://www.microsoft.com/en-us/lync/pricing-licensing.aspx
The cost of an Enterprise CAL has come down but no longer includes telephony functions. Telephony in Lync server requires the new Plus CAL in addition to the Standard and Enterprise CALs. At the bottom there is the matrix of what each CAL covered both on R2 and Lync
If you have the Microsoft Enterprise CAL suite the Lync Standard and Enterprise CALs are included but the Plus CAL is still an addition.
The Lync client software is available either standalone or is included in the Office Professional Plus 2010 product.
Depending on your current Software Assurance your current OCS 2007R2 licenses as a qualifying license for Lync.
Having read details it has generated a lot of questions in mind and once I have answers I will update everyone.
IM and Presence
Audio, Video and Web Conferencing
Enterprise Voice
UC by UC 