Yesterday Microsoft released Skype for Business thru Windows update and click-to-run.

On-prem environments must be updated with the following IF you want to use the new gui.

Lync 2010 server with CU 4.0.7577.710 https://support.microsoft.com/fi-fi/kb/2493736
Lync 2013 server with CU 5.0.8308.857 https://support.microsoft.com/en-us/kb/3018158

Then you have an option to Enable with Get-CsClientPolicy | Set-CsClientPolicy -EnableSkypeUI $true and disable with Get-CsClientPolicy | Set-CsClientPolicy -EnableSkypeUI $false

New features compared to the old.

Feature
Skype UI
Lync UI
Skype First Run Intro
x
New Emoticons
x
x
Call Monitor
x
Call via work (on Skype for Business Server)
x
Remote Call Control
x
Rate my Call end of call surveys
x
x
Server Side conversation history (on Skype for Business Server)
x
x
Skype Consumer Video interop
x
x