Finally I had time to try S4B server installation. But unfortunately it ends into error:
Prerequisite not satisfied: Before you install Skype for Business Server 2015, you must install an update for Windows Server 2012 R2. For details about the update, see Microsoft Knowledge Base article 2982006, "IIS crashes occasionally when a request is sent to a default document in Windows 8.1 or Windows Server 2012 R2" at http://go.microsoft.com/fwlink/?LinkId=519376
Ok.. easy...except, the Link on the page: "Hotfix Download is available" leads me to the page saying: "Sorry, the page you requested is not available".
There seems to be some bug in the installation code, as the files listed on the hotfix are already updated on my server.
Any idea how to get this