I had questions from engineers and customers around a good start for GroupChat Deep-Dive.

 

http://technet.microsoft.com/en-us/library/ee303783(office.13).aspx

 

This is a very recent addition, which gives a good Overview.

 

Group Chat Call Flows are outlined and explained here:

 

http://technet.microsoft.com/en-us/library/ee323524(office.13).aspx

 

Hope this is useful to all.