Lync users can connect to Skype from Lync 2010 or Lync 2013, including any of the 2013 mobile clients. Skype users need to have the latest Skype client for their particular platform, downloadable from Skype.com. Currently, only Windows and Mac desktop clients are supported; the Windows 8, Windows Phone 8, Linux and other mobile platforms will be added "soon."
In addition, for the Skype-Lync connectivity to work, Skype users must sign in to Skype with a Microsoft account (formerly Windows Live ID) to communicate with their Lync contacts.
While today's availability announcement for phase one of the integration comes ahead of the self-imposed June 30 deadline Microsoft set for itself, it's still later than many had expected.
Lync is Microsoft's unified communications platform for business users. It includes corporate IM, VOIP and conferencing capabilities. Skype is Micrsosoft's unified communications platform for consumers. Late last year, Microsoft moved the Lync team under the Skype team, so that Lync reported to Tony Bates, the President of Skype. (That said, Lync still reports its financial results as part of the Microsoft Business Division, not the Entertainment & Devices unit, which is where the Skype division reports.)