We are in the process of rolling a POC for Lync 2013 Server out. My windows clients connect flawlessly with the 2013 Client.
When I set Lync up, I did a self signed cert from my DC which up until this point was now when we tried to get a couple of mac clients to connect.
"Sign in to Microsoft Lync failed because the service is not available or you may not be connected to the internet." is the error message.
OSX 10.6.8 and is as up to date as apple will allow it.