The Lync client for Mac 2011 is now available for download from the Microsoft Online Portal downloads page (https://portal.microsoftonline.com/download/).
You will only see the option appear if you’re running Safari.
Having used the client myself and set it up for customers I found it’s a breeze and almost as fully featured as the Windows version.
One quick gotcha though – it doesn’t support switching audio devices when loaded. You actually need to exit the program, change your audio device in the Mac control panel, then load Lync for Mac again.