The last part of today was Persisten Chat Server. This replace to old group chat server in Lync2010.
The good news is that we don't need a separate client.
We can if you have installed Enterprise Edition, then we can build a pool of Chat servers.
With Chat server you can build Project rooms for you company, but be aware that you can not invite federated users.
Chat server can connect to SQL Express or your regular SQL. It's up to you but since SQL Express has limited functionality due to database size in SQL 2012 Express the limitation is 10GB pr database.
The Lync client after you have been connected to rooms then they will show as a catalog in the client.
Tomorrow we have the third day and more information will come then.