You can read more about it in the official blog found here, and download the actual software here. You have to use a Microsoft account to login and register to download.
The version number in the about box will read:
Microsoft Lync 2013 (15.0.4707.1000) MSO (15.0.4707.1000)
I immediately got the chance to test some of my favorite Lync apps with the new client.
- My Link Lync presence to Skype still worked.
- My Kuando Busylight still worked.
- My Profiles For Lync 2013 - Swedish edition still worked.
Among many new nice features in this new client are
- New look and feel
- Call via Work
- Skype directory integration
- Dual user experience
- Call Monitor
- Rate My Call
- Quick access to call controls
And you can read more about them and the client here.
The client will work with your current Lync 2013 Server or even Lync 2010 server. Some of the new features and functions will require the Skype for business Server 2015 or the forthcoming changes in Office 365 to rewamp Lync online into Skype for business online.