After installing Lync 2013 with October 2013 Update and rebooted the FrontEnd server, we had an issue that the Frontend service was hanging in starting.
To resolve this we had to remove two Thwate certificate that did not have the same Issued From= Issued To. This article on Technet tells about it and how to fix it. .
This also is the same issue for Windows 2012R2. And with the October 2013 update for Lync 2013, Windows 2012R2 server is supported.